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IGCSE Physics notes

  1. 1. Physics for the Cambridge iGCSE Syllabus B. Murphy
  2. 2. Contents Topic Topic 1 Topic 2 Topic 3 Topic 4 Topic 5 Page Number General Physics Past Paper Questions Thermal Physics Past Paper Questions Waves Past Paper Questions Electricity & Magnetism Past Paper Questions Atomic Physics Past Paper Questions Appendix Syllabus 2 26 70 83 108 120 146 173 214 221 234 1
  3. 3. Topic 1: General Physics 1 Length • Length is a distance measurement and its SI unit is the metre (m). • Length is usually measured with a rule, a tape or a trundle wheel. • Small lengths are measured with a micrometer or callipers where a greater precision is available. • In certain circumstances, average lengths can be found be measuring a number of distances together then dividing by the number of objects eg a ream of paper. 2 Time • Time is usually measured with a stopclock. Human timing is not precise because of reaction times. • The SI unit for time is seconds (s). • For repeated events, an average time can be found by measuring a number of repeats then dividing by the number of cycles eg. a pendulum. 3 2
  4. 4. Speed • Speed tells us how fast something is moving. • It is measured in m/s. • Average speed is calculated using: Average Speed (m s) = Distance moved (m) time taken (s) 4 Examples • A sprinter runs 100m in 10s. Calculate his average speed. • A bird flies 60m in 5s. Calculate its average speed. • Pupils measured their times taken to travel different distances doing various exercises. Their results are recorded in the table. Complete the table. Exercise Distance (m) Time (s) Running 70 12 Walking 10 35 Hopping 50 Speed (m/s) 110 5 Acceleration • Acceleration tells us how quickly something is changing its speed. • It is measured in m/s2. • Acceleration is calculated using: Average Acceleration (m s 2 ) = Change in speed ( m s ) time taken (s) Example: • A motorbike goes from 10m/s to 35 m/s in 8s. Calculate his acceleration 6 3
  5. 5. Distance/time graphs • A Distance/time graph is a way of representing motion. distance Acceleration stationary Constant speed (fast) Constant speed (slow) time 7 Calculations with distance/ time graphs • Speed is given by the gradient of the distance/time graph. 8 Distance/time graph questions • Describe the motion of the following bodies: (a) (b) d (c) d t d t t 9 4
  6. 6. Distance/Time Graph questions • Calculate the speeds of the car and the bike below: Distance (m) 500 375 Car Bike 250 125 0 0 5 10 15 20 25 10 Time (s) Speed/time graphs • A Speed/time graph is an alternative way of representing motion. speed Non-Uniform Acceleration Constant speed Rapid acceleration Gradual acceleration Stationary time 11 Calculations with speed/time graphs • Acceleration is given by the gradient of the speed/ time graph. • Distance is given by the Area under the speed/time graph. 12 5
  7. 7. Speed/time graph questions Describe the motion of the following bodies: • (a) (b) v (c) v v t t t 13 Speed/time calculation. • (a) Find the acceleration of the bike in the first 10s. • (b) Find the distance moved by the bike in the first 20s. Motion of a bike 15.00 Speed (m/s) 11.25 7.50 3.75 0 0 5 10 15 20 14 time (s) The Ticker-Timer Ticker Tape Ticker Timer • The ticker-timer runs at 50Hz. It puts 50 dots on the tape every second. • If the tape moves quickly, the dots are widely spaced. • If the tape moves slowly, the dots are close 15 6
  8. 8. Ticker Tape Slow moving ticker-tape Fast moving ticker-tape 16 Charts • By cutting the tape into 5 space strips and arranging them side-by-side we can get a chart representing the motion. • Each strip will represent 0.1s of motion. 17 Typical Shapes of Charts 18 7
  9. 9. Calculations • Since each strip represents 0.1s of motion, and we can measure the length of the strips in cm, we can use speed=distance/time to calculate the speeds. 19 Scalars and Vectors • A SCALAR quantity has a size (Magnitude), but no direction. • Examples of scalar Quantities are temperature, time, energy and power. • A VECTOR quantity has both a magnitude and a direction. Vectors are often represented with an arrowed line. The direction of the arrow is the direction of the vector and the length of the line represents the size of the vector. • Examples of vectors are force, momentum and velocity. F 20 2 1 Big Stone Small Stone Paper Tray 3 Small Stone Paper Coin Vacuum Sand Bucket Sand Bucket 21 8
  10. 10. Gravity • Experiment 1 • • • Both Stones Land at the same time. Gravity makes them fall at the same rate. Experiment 2 • • • Stone landed first. Air Resistance slowed down the paper tray. Experiment 3 • Both coin & paper land at the same time. 22 Weight and Mass • Weight is a force. It tells us how heavy something is. It is measured in newtons (N). It changes depending upon the size of gravity. (Trip to the moon) • Mass tells us how much substance there is in an object. It is measured in kilograms (kg). It never changes. • On Earth we multiply mass by 10 to get weight. 23 Density • Density tells us how compact the mass is in a material. • It is given by: Density ( kg m 3 ) = mass(kg) volume(m 3 ) or Density ( g cm 3 ) = mass(g) volume(cm 3 ) •Stick to one set of units. •Water has a density of 1000 kg/m3 or 1 g/cm3. •Materials with a smaller density than water will float, materials with a higher density than water will sink. 24 9
  11. 11. Density Calculation Complete the following table: Object Density (kg/ m3) B 2000 2 8000 C Volume (m3) 4000 A Mass (kg) D 4 1000 2000 4 a) Which object has the greatest mass? b) Which has the smallest volume? c) Which objects could be made of the same substance? d) Which object would float on water? 25 Irregular objects • The volume of a liquid can be determined using a measuring cylinder. • The volume of irregular objects has to be found by displacement. 26 Hooke’s Law • Hooke’s Law states that the extension in a spring is proportional to the load applied. load α extension or F = kx The constant of proportionality is called the Spring Constant. 27 10
  12. 12. Extension/Force Graphs • A graph can be plotted to show how Force varies with extension for a spring. • The graph shows proportionality up to a point called the ‘proportionality limit’. • With increased extension, the spring will reach a point at which it will not return to its original shape. This is called the elastic limit. The spring shows ‘plastic’ behaviour beyond here. 28 Load/Extension Graphs • A graph can be plotted to show how extension varies with load for a spring. • The graph shows proportionality up to a point called the ‘proportionality limit’. • With increased load, the spring will reach a point at which it will not return to its original shape. This is called the elastic limit. The spring shows ‘plastic’ behaviour beyond here. 29 Extension/Force Graphs extension Proportionality Limit Linear Region 0 Load 30 11
  13. 13. Newton’s 1st Law • If the forces around an object balance (resultant 0N), then it will either: • Remain at rest or • • Move at a constant speed in a straight line. (This is the same as saying constant velocity). 31 Examples of 1st Law Normal Normal Air Air Gravity Gravity Remains at rest Moves at a constant speed in a straight line 32 Oil Tube Experiment Fluid Resistance Falls at a constant speed in a straight line. Gravity 33 12
  14. 14. Unbalanced Forces • If the forces around an object do not balance, then they will cause the object to accelerate (or decelerate). • The rate of the acceleration depends upon the mass of the object. • The quantities are linked by the following equation: F(N ) = m(kg) × a(m s 2 ) 34 Questions • 1. What will be the Force needed to produce an acceleration of 2m/s2 on a mass of 4kg? • 2. What will be the Force needed to produce an acceleration of 5m/s2 on a mass of 42kg? • 3. What will be the acceleration produced when a Force of 50N acts upon a mass of 10kg? 35 Newton’s Laws Calculation P 6000 N Q 400 N 10 000 N A front wheel drive car is travelling at constant velocity. Q is the force of the air on the moving car. P is the total upward force on both front wheels. (a) Explain why P= 4 000N, Q= 400N (b) Calculate the mass of the car. (c) The 400 N driving force to the left is suddenly doubled. (i) Calculate the resultant forward driving force. (ii) Calculate the acceleration of the car. (iii) Sketch a graph showing how the velocity of the car changes with time (start the graph just before the driving force is doubled.) 13 36
  15. 15. Circular Motion • When an object is moving in a circle, it must be experiencing a force TOWARDS THE CENTRE of the circle. • We call this the CENTRIPETAL Force. • This should not be confused with CENTRIFUGAL Force. • The centripetal force is directed at right angles to the object’s velocity. object’s path direction of force 37 Questions • For each of the following examples, draw a sketch to show the situation, name the force providing the circular motion, and indicate its direction: • A) The Earth orbiting the Sun. • B) A car rounding a bend. • C) A hammer-thrower winding into his throw. 38 Moments • A moment is a turning force. • It is given by: Moment(Nm) = Force(N ) × distance(m) 39 14
  16. 16. Example • Calculate the moment produced: 0.1m 100N 40 The Principle of Moments • If a lever is balanced (in equilibrium) then the total clockwise moments equal the total anti-clockwise moments. It will not move. • Because of Newton’s 1st Law, the forces must also balance. Clockwise moments Anti-clockwise moments 41 Results Left-Hand Side Right-Hand Side Weight Distance 8 4 ? 3 4 ? 6 5 2 2 ? 6 3 ? 2 Weight Distance 2 Wxd Wxd 42 15
  17. 17. Moments Questions • 1. Explain why a mechanic would choose a long-arm spanner to undo a tight nut. • 2. In the following diagram, what is the weight of X ? 20 cm X 25 cm 4N 43 Uses of Levers • Spanner • Nutcracker • Scissors 44 Centre of Mass • Centre of mass is the point on an object that is the ‘average’ position of the mass of the object. • The centre of gravity is a point on all objects through which forces appear to act. • The two points are the same. • The centres of mass of regular objects are obvious. They always lie on a line of symmetry. • They are the point under which we place a pivot to balance the object. 45 16
  18. 18. Regular Objects 46 Stability • Stability tells us how secure something is on the ground. • If something is stable, then it will not topple easily. • There are two factors to consider when changing the stability of an object: • • • The area of the object’s base. The position of the centre of mass of the object. A stable object will have a BIG base, and a LOW centre of gravity. 47 Simple Addition • If two vectors are parallel, then they can be simply added or subtracted to give a resultant. 3N 5N RESULTANT 2N 48 17
  19. 19. 2D-Addition • If the vectors are not parallel we have to draw a scale diagram and add the vectors to give a resultant. RESULTANT 3m/s 2m/s 2m/s 3m/s 49 Examples • 1. A plane flies North at 40m/s. The wind blows to the East at 15 m/s. Calculate the overall velocity. • 2i). A falling ball has a weight of 10N and and air resistance of 2N. What the effective downward force on it? • ii) A wind blows to the left with a force of 2N. Using a vector diagram, calculate the resultant force on the ball. 50 Heat Sound Kinetic Electricity Elastic Potential Energy Energy Forms Light Gravitational Potential Energy Chemical Potential Energy 51 18
  20. 20. Energy Transfers • When any physical process takes place, there is a transfer of energy from one form to another. • This can be shown in an energy flow diagram: Light Electricity T.V Sound Heat 52 Examples of Energy Transfers • A burning match • A lightbulb • A petrol lawnmower • A car • Headphones • A microphone • A waterfall 53 Kinetic Energy • All objects that are moving have kinetic energy. • It depends on the mass of the object and its speed. • It is measured in joules. KE = 1 2 mv 2 54 19
  21. 21. Gravitational Energy • Gravitational energy is stored in objects that are at a height. • It depends upon the mass of the object, and how high the object is. • It measured in joules. GPE = mgh 55 The Principle of the Conservation of Energy • Energy cannot be created or destroyed, it simply moves from one form to another. • When energy moves from one form to another, the total AMOUNT of energy remains the same. • A certain amount of heat energy is always lost to the surroundings in any process. 56 Efficiency • Efficiency tells us how effective a process or energy transfer is. • The more useful energy that is produced, for the least input energy, the more efficient the process is. • Efficiency has no unit, and can be expressed as a decimal or percentage. • It can be the ratio of power output to input, or energy output to input for a process Efficiency = output (×100) input 57 20
  22. 22. Work Done • Work is a type of energy change and is measured in Joules. • For work to be done, a force must be acting upon an object as it moves through a distance. • The Work Done is given by: Work Done (J )=Force(N ) × Distance(m) 58 Power • Power is the rate at which energy is transferred. • It is also the rate at which Work is done. • The unit for Power is Watts (W). • Power is calculated from either: Power(W )= Energy Change(J ) Time Taken(s) or Power(W )= Work Done(J ) Time Taken(s) 59 Calculating Personal Power height time weight • Measure your weight in newtons. • Measure the height of the steps in metres. • Measure the time taken to climb the steps in seconds. • Calculate the Work Done in joules. • Calculate the Power of your legs in Watts. 60 21
  23. 23. Pressure • Pressure tells us how concentrated a force is. • It is calculated from: Pressure( N m 2 )= Force(N ) Force(N ) 2 or Pressure( N cm )= 2 Area(m ) Area(cm 2 ) Stick to one set of units 61 Examples 2cm 1cm 20g 1cm 1. Calculate the Volume of the block. 2. Calculate the block’s density. 3. Calculate the block’s weight. 4. Calculate the area in contact with the ground. 62 Examples • Why do camels have large flat feet? • Why is it easier to walk in snow shoes in the snow? 63 22
  24. 24. Pressure in Liquids Pressure in a liquid is due to the weight of the liquid above a point. Pressure increases with depth. Pressure will also increase with density of liquid (more weight). P = ρ gd We can calculate pressure from: 64 Direction • The pressure in a liquid acts in ALL directions equally at a point. • This is why bubbles are spherical. 65 Questions • 1a). Draw a diagram of the cross section of a dam. • b) Explain why it has this shape. • 2. Calculate the pressure on a scuba diver at a depth of 20m. (The density of water is 1000kg/m3) • 3. Describe a demonstration to show that Pressure increases with depth in a liquid. 66 23
  25. 25. Non-Renewable Energy Resources • Non-Renewable resources are resources that are used up and cannot be easily replaced. Examples are fossil fuels and Nuclear fuels. 67 Renewable Energy Resources • Renewable Energy Resources are energy resources that keep running and do not run-out easily. 68 • Nuclear Fusion Safety • Pollution • Problems Energy usage • Transport • Electricity The Energy Crisis • Fossil Fuels • Pollution • Depletion Renewable Alternatives • Advantages • Unreliable • Not Controllable • Energy Density Nuclear Fission • Energy Density • Pollution • Safety 69 24
  26. 26. General Physics Quantity and symbol Scalar Quantities Vector Quantities Average Speed, s Velocity Acceleration, a Mass, m Weight, W, F Density, ρ Force, F Load, (Hookes law) Moment Equilibrium Work done, W, E Kinetic energy, KE Definition/Word equation Scalar quantities only have a magnitude. Vector quantities have a magnitude, a direction and a point of application. Speed is the rate of change of distance. It is a scalar quantity. Speed = Total distance Total time For constant acceleration situations, the average speed is also equal to the average of the initial and final speeds. s = initial speed + final speed 2 Velocity is the rate of change of displacement. It is speed in a given direction. A vector quantity. Acceleration is the rate of change of velocity. Acceleration = Final velocity – initial velocity Time Mass is a property of a body that resists change in motion. Weight is the force on a mass due to the gravitational field of the Planet. It changes from planet to planet. Weights can be compared using a balance. Weight = mass x acceleration due to gravity Weight = mass x gravitational field strength Density is the mass per unit volume. Density = mass volume A force is a push or a pull; it can change the shape, direction, and/or speed of an object. Force = mass x acceleration Load = spring constant x extension Load α extension A moment is the turning affect of a force. Moment = force x perpendicular distance from the pivot When there is no resultant force AND no resulting turning affect, a system is in equilibrium. Work done = Force x distance in the direction of the force = change in energy Kinetic energy is the energy of a body due to its motion. Kinetic energy = ½ x mass x velocity2 25 Symbol equation Units s=d t s=u+v 2 m/s cm/s km/h m/s cm/s km/h a= v–u t m/s2 W=mxg Newtons, N ρ=m V Kg/m3 g/cm3 F=ma Newtons, N F=kl F α l Newtons, N Moment = F d Nm W = F d = ΔE Joules, J KE = ½ m v2 Joules, J
  27. 27. Gravitational energy, GPE Efficiency Power, P Gravitational potential energy is the energy of a body due to its position in the gravitational field. Gravitational energy =mass x acceleration due to gravity x height gained/lost Efficiency = useful output x 100% total input Power is the rate at which energy is converted. Power = work done time taken Power = energy change time taken GPE = m g h % P=E t Pressure, p, P Pressure = force area P=F A Fluid Pressure, p, P Pressure = density of fluid x acceleration due to gravity x height of fluid above P=ρgh 26 Joules, J Watts, W N/m2 Pascals, Pa millibar N/m2 Pascals, Pa Millibar
  28. 28. iGCSE Physics Past Paper Questions Paper 1 Compilation General Physics 27
  29. 29. 2 11. The diagram shows the level of liquid in a measuring cylinder. cm3 30 liquid 20 What is the volume of the liquid? A 24 cm3 B 28 cm3 C 29 cm3 D 32 cm3 2 A cylindrical can is rolled along the ruler shown in the diagram. 2. final position starting position can rolled mark on can 0 cm 5 10 15 20 The can rolls over twice. What is the circumference (distance all round) of the can? A 13 cm B 14 cm C 26 cm D 0625/1/M/J/02 28 28 cm 25 30 cm
  30. 30. 3 33. The graph shows how the speed of a car changes with time. Q speed P O R time Which of the following gives the distance travelled in time interval OR? A the area OPQR B the length PQ C the length (QR – PO) D the ratio QR/PO 4 4. A snail crosses a garden path 30 cm wide at a speed of 0.2 cm/s. movement of snail 30 cm snail How long does the snail take? A 5. 5 B 0.0067 s 6.0 s C 15 s D 150 s What are correct units used for mass and for weight? mass weight A kg kg B kg N C N kg D N N 0625/1/M/J/02 29 [Turn over
  31. 31. 4 66. Two objects X and Y are placed on a beam as shown. The beam balances on a pivot at its centre. Y X pivot What does this show about X and Y? A They have the same mass and the same density. B They have the same mass and the same weight. C They have the same volume and the same density. D They have the same volume and the same weight. 7. A shop-keeper places two identical blocks of cheese on a set of scales and notices that their 7 combined mass is 240 g. Each block measures 2.0 cm x 5.0 cm x 10.0 cm. g What is the density of the cheese? A 0.42 g / cm3 B 0.83 g / cm3 C 1.2 g / cm3 D 2.4 g / cm3 8 8. The table shows the length of a wire as the load on it is increased. load / N length / cm 0 50.0 10 20 30 52.1 54.1 56.3 Which subtraction should be made to find the extension caused by the 20 N load? A 54.1 cm – 0 cm B 54.1 cm – 50.0 cm C 54.1 cm – 52.1 cm D 56.3 cm – 54.1 cm 0625/1/M/J/02 30
  32. 32. 5 99. A child tries to push over a large empty oil drum. Where should the drum be pushed to topple it over with least force? A B C D 10. Which device is designed to convert chemical energy into kinetic energy (energy of motion)? 10 A an a.c. generator B a battery-powered torch C a car engine D a wind-up mechanical clock 11. A ball is released from rest and rolls down a track from the position shown. 11 What is the furthest position the ball could reach? C ball starts here B D A 0625/1/M/J/02 31 [Turn over
  33. 33. 6 12 Two sharp nails and two blunt nails are held on a piece of wood. Each nail is hit with the same 12. hammer with the same amount of force. When it is hit, which nail causes the greatest pressure on the wood? A B hammer sharp nails C D hammer blunt nails 13. 13 The diagram shows a manometer connected to a container of carbon dioxide. container carbon dioxide 5 cm mercury manometer Which statement correctly describes the pressure exerted by the carbon dioxide? A It is equal to the atmospheric pressure. B It is equal to 5 cm of mercury. C It is equal to 5 cm of mercury above atmospheric pressure. D It is equal to 5 cm of mercury below atmospheric pressure. 0625/1/M/J/02 32
  34. 34. 2 14. A glass tank contains some water. 1 V water T Q U S R The length QR and the width RS of the tank are known. What other distance needs to be measured in order to be able to calculate the volume of the water? A B ST C SV D TU TV 2 15. A stopwatch is used to time a race. The diagrams show the watch at the start and at the end of the race. start 55 end 60 5 55 10 50 40 35 30 45.7 s B 46.0 s 15 40 25 C 46.5 s D 0625/01/M/J/03 33 47.0 s 20 seconds 35 How long did the race take? A 10 45 20 seconds 5 50 15 45 60 30 25
  35. 35. 3 16. The diagram shows a speed-time graph for a body moving with constant acceleration. 3 speed 0 time 0 What is represented by the shaded area under the graph? A acceleration B distance C speed D time 17. A tunnel has a length of 50 km. A car takes 20 min to travel between the two ends of the tunnel. 4 What is the average speed of the car? A 2.5 km / h B 16.6 km / h C 150 km / h D 1000 km / h 18. Which statement is correct? 5 A Mass is a force, measured in kilograms. B Mass is a force, measured in newtons. C Weight is a force, measured in kilograms. D Weight is a force, measured in newtons. 0625/01/M/J/03 34 [Turn over
  36. 36. 4 6 19. Three children, X, Y and Z, are using a see-saw to compare their weights. X Y Y Z X Z Which line in the table shows the correct order of the children’s weights? heaviest ←→ lightest A X Y Z B X Z Y C Y X Z D Y Z X 20. What apparatus is needed to determine the density of a regularly-shaped block? 7 A a balance and a ruler B a balance and a forcemeter (spring balance) C a measuring cylinder and a ruler D a measuring cylinder and a beaker 21. A spring is suspended from a stand. Loads are added and the extensions are measured. 8 spring stand loads rule Which graph shows the result of plotting extension against load? 0 0 load 0 0 0 load 0625/01/M/J/03 35 extension D extension C extension B extension A 0 load 0 0 load
  37. 37. 5 22. A student uses a stand and clamp to hold a flask of liquid. 9 Which diagram shows the most stable arrangement? A B C D 10 What is the source of the energy converted by a hydro-electric power station? 23. A hot rocks B falling water C oil D waves 24. 11 A labourer on a building site lifts heavy concrete blocks onto a lorry. Lighter blocks are now lifted the same distance in the same time. What happens to the work done in lifting each block and the power exerted by the labourer? work done in lifting each block power exerted by labourer A decreases decreases B decreases remains the same C increases increases D remains the same increases 0625/01/M/J/03 36 [Turn over
  38. 38. 6 25. 12 The diagram shows an instrument used to measure gas pressure. liquid What is the instrument called? A ammeter B barometer C manometer D thermometer 13 The diagrams show two divers swimming in the sea and two divers swimming in fresh water. Sea 26. water is more dense than fresh water. On which diver is there the greatest pressure? 0m 0m sea water A 2m 4m fresh water C 2m B 6m 4m 6m 14 When water evaporates, some molecules escape. 27. Which molecules escape? A the molecules at the bottom of the liquid with less energy than others B the molecules at the bottom of the liquid with more energy than others C the molecules at the surface with less energy than others D the molecules at the surface with more energy than others 0625/01/M/J/03 37 D
  39. 39. 2 1 The diagram shows a me asuring cylinder. 28. 100 90 80 70 60 50 40 30 20 10 Which unit would be most suitable for its scale? A mm 2 mm 3 B cm 2 C D cm 3 29. A piece of cotton is me asured betwe en two points on a ruler. 2 cotton cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 When the length of cotton is wound closely around a pen, it goes round six times. six turns of cotton pen What is the distance once round the pen? A 2.2 cm U C L E S 2004 B 2.6 cm C 13.2 cm 0625/01/M/J/04 38 D 15.6 cm 16
  40. 40. 3 3 The diagram shows the speed-time graph for an object moving at constant speed. 30. 2 speed m/s 1 0 0 1 2 4 3 time / s What is the distance travelled by the object in the first 3 s? A 1.5 m B 2.0 m C 3.0 m D 6.0 m 4 31. A small steel ball is dropped from a low balcony. Ignoring air resistance, which statement describes its motion? A It falls with constant acceleration. B It falls with constant speed. C It falls with decreasing acceleration. D It falls with decreasing speed. 32. Which statement about the mass of a falling object is correct? 5 A It decreases as the object falls. B It is equal to the weight of the object. C It is measured in newtons. D It stays the same as the object falls. © UCLES 2004 0625/01/M/J/04 39 [Turn over
  41. 41. 4 6 The weights of four objects, 1 to 4, are compared using a balance. 33. 2 2 1 4 2 3 Which object is the lightest? A B object 1 C object 2 D object 3 object 4 7 34. Which of the following is a unit of density? A cm3 / g B g / cm2 C g / cm3 D kg / m2 8 A piece of card has its centre of mass at M. 35. Which diagram shows how it hangs when suspended by a thread? A B C D M M M M 9 An experiment is carried out to measure the extension of a rubber band for different loads. 36. The results are shown below. load / N length / cm 0 1 15.2 16.2 0 1.0 extension / cm 2 3 18.6 2.1 3.4 Which figure is missing from the table? A 16.5 © UCLES 2004 B 17.3 C 17.4 0625/01/M/J/04 40 D 18.3
  42. 42. 5 36. 10 The diagram shows a man diving into water. 37. Which form of energy is incre asing as he falls? A chemical B gravitational C kinetic D strain 38. A boy and a girl run up a hill in the same time. 11 boy weighs 600 N girl weighs 500 N The boy weighs more than the girl. Which statement is true about the power produced? A The boy produces more power. B The girl produces more power. C They both produce the same power. D It is impossible to tell who produces more power. © UCLES 2004 0625/01/M/J/04 41 [Turn over
  43. 43. 6 39. 12 The diagram shows a simple mercury barometer. The barometer re ading is h cm of mercury. S h mercury 40. What is the pressure at S? A approximately z ero B atmospheric pressure C atmospheric pressure + h cm of mercury D h cm of mercury 41. 13 Two boys X and Y e ach have the same total weight and are standing on soft ground. X Y Which boy is more likely to sink into the soft ground and why? boy more likely to sink pressure on soft ground A X larger than Y B X smaller than Y C Y larger than X D Y smaller than X U C L E S 2004 0625/01/M/J/04 42
  44. 44. 2 42. 1 A decorator wishes to calculate the area of a bathroom tile so that he can estimate the amount of adhesive that he needs to buy. What must he use? A a measuring cylinder only B a ruler only C a measuring cylinder and a clock only D a measuring cylinder and a ruler only 2 43. The three balls shown are dropped from a bench. aluminium lead wood Which balls have the same acceleration? A aluminium and lead only B aluminium and wood only C lead and wood only D aluminium, lead and wood 44. 3 A car accelerates from traffic lights. The graph shows how the car’s speed changes with time. speed m/s 20 0 0 10 time / s How far does the car travel before it reaches a steady speed? A 10 m © UCLES 2005 B 20 m C 100 m 0625/01/M/J/05 43 D 200 m
  45. 45. 3 45. 4 Which statement is correct? A B The mass of a bottle of water is measured in newtons. C The weight of a bottle of water and its mass are the same thing. D 5 The mass of a bottle of water at the North Pole is different from its mass at the Equator. The weight of a bottle of water is one of the forces acting on it. Two blocks X and Y are placed on a beam as shown. The beam balances on a pivot at its centre. Y X pivot 46. What does this show about X and Y? A They have the same mass and the same density. B They have the same mass and the same weight. C They have the same volume and the same density. D They have the same volume and the same weight. 6 The masses of a measuring cylinder before and after pouring some liquid into it are shown in the 47. diagram. cm3 cm3 200 200 100 100 liquid mass = 80 g mass = 180 g What is the density of the liquid? A 100 g / cm3 120 © UCLES 2005 B 100 g / cm3 140 C 180 g / cm3 120 0625/01/M/J/05 44 D 180 g / cm3 140 [Turn over
  46. 46. 4 7 48. A girl and a boy are pulling in opposite directions on a rope. The forces acting on the rope are shown in the diagram. girl boy 200 N 150 N rope 49. Which single force has the same effect as the two forces shown? A 50 N acting towards the girl B 350 N acting towards the girl C 50 N acting towards the boy D 350 N acting towards the boy 8 Objects with different masses are hung on a 10 cm spring. The diagram shows how much the 50. spring stretches. 10 cm 20 cm 30 cm 100 g M The extension of the spring is directly proportional to the mass hung on it. What is the mass of object M? A 110 g © UCLES 2005 B 150 g C 200 g 0625/01/M/J/05 45 D 300 g
  47. 47. 5 51. 9 What is designed to change electrical energy into kinetic energy? A capacitor B generator C motor D transformer 10 52. A power station uses nuclear fission to obtain energy. In this process, nuclear energy is first changed into A chemical energy. B electrical energy. C gravitational energy. D internal energy. 11 A ball is released from rest and rolls down a track from the position shown. 53. What is the furthest position the ball could reach? C ball starts here B D A © UCLES 2005 0625/01/M/J/05 46 [Turn over
  48. 48. 6 54. 12 A water manometer is used to measure the pressure of a gas supply to a house. It gives a reading of h cm of water. gas supply h cm 55. Why is it better to use water rather than mercury in this manometer? A h would be too large if mercury were used. B h would be too small if mercury were used. C The tube would need to be narrower if mercury were used. D The tube would need to be wider if mercury were used. 13 A farmer has two carts. The carts have the same weight, but one has four narrow wheels and the 56. other has four wide wheels. narrow wheel wide wheel In rainy weather, which cart sinks le s s into soft ground, and why? cart wheels why A narrow greater pressure on the ground B narrow less pressure on the ground C wide greater pressure on the ground D wide less pressure on the ground © U C L E S 2005 0625/01/M/J/05 47
  49. 49. 2 57. 1 A measuring cylinder contains some water. When a stone is put in the water, the level rises. cm3 200 cm3 200 150 150 100 100 50 50 stone What is the volume of the stone? A 50 cm3 B 70 cm3 75 cm3 C D 125 cm3 258.The graph represents the movement of a body accelerating from rest. 10 speed m/s 8 6 4 2 0 1 2 3 4 5 time / s 59. After 5 seconds how far has the body moved? A 3 2m B 10 m C 25 m D 50 m A child is standing on the platform of a station, watching the trains. A train travelling at 30 m / s takes 3 s to pass the child. What is the length of the train? A 10 m © UCLES 2006 B 30 m C 90 m 0625/01/M/J/06 48 D 135 m
  50. 50. 3 60. 4 Below are four statements about the effects of forces on objects. Three of the statements are correct. Which statement is incorrect? A A force can change the length of an object. B A force can change the mass of an object. C A force can change the shape of an object. D A force can change the speed of an object. 61. 5 A simple balance has two pans suspended from the ends of arms of equal length. When it is balanced, the pointer is at 0. arm pivot pointer 0 pan X pan Y Four masses (in total) are placed on the pans, with one or more on pan X and the rest on pan Y. Which combination of masses can be used to balance the pans? A 1 g, 1 g, 5 g, 10 g B 1 g, 2 g, 2 g, 5 g C 2 g, 5 g, 5 g, 10 g D 2 g, 5 g, 10 g, 10 g 6 62. A person measures the length, width, height and mass of a rectangular metal block. Which of these measurements are needed in order to calculate the density of the metal? A mass only B height and mass only C length, width and height only D length, width, height and mass © UCLES 2006 0625/01/M/J/06 49 [Turn over
  51. 51. 4 63. 7 Two forces act on an object. In which situation is it impossible for the object to be in equilibrium? A The two forces act in the same direction. B The two forces act through the same point. C The two forces are of the same type. D The two forces are the same size. 64. The diagram shows four models of buses placed on different ramps. 8 centre of mass centre of mass centre of mass centre of mass 65. How many of these models will fall over? A 9 1 B 2 C 3 D 4 Which form of energy do we receive directly from the Sun? A chemical B light C nuclear D sound 10 66. A labourer on a building site lifts a heavy concrete block onto a lorry. He then lifts a light block the same distance in the same time. Which of the following is true? work done in lifting the blocks power exerted by labourer A less for the light block less for the light block B less for the light block the same for both blocks C more for the light block more for the light block D the same for both blocks more for the light block © UCLES 2006 0625/01/M/J/06 50
  52. 52. 5 67. 11 The diagram shows a thick she et of glass. Which edge must it stand on to cause the gre atest pressure? A B D C 68. 12 A manometer is being used to me asure the pressure of the gas inside a tank. A, B, C and D show the manometer at different times. At which time is the gas pressure inside the tank gre atest? A B C D gas 13 Brownian motion is se en by looking at smoke particles through a microscope. How do the smoke particles move in Brownian motion? A all in the same direction B at random C in circles D vibrating about fixed points © U C L E S 2006 0625/01/M/J/06 51 [Turn over
  53. 53. iGCSE Physics Past Paper Questions Paper 3 Compilation General Physics 52
  54. 54. 2 1 1. A group of students attempts to find out how much power each student can generate. The students work in pairs in order to find the time taken for each student to run up a flight of stairs. The stairs used are shown in Fig. 1.1. finishing point starting point Fig. 1.1 (a) Make a list of all the readings that would be needed. Where possible, indicate how the accuracy of the readings could be improved. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [4] (b) Using words, not symbols, write down all equations that would be needed to work out the power of a student. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) (i) When the student has reached the finishing point and is standing at the top of the stairs, what form of energy has increased to its maximum? ................................................................................................................................... (ii) Suggest why the total power of the student is greater than the power calculated by this method. ................................................................................................................................... ................................................................................................................................... [3] 0625/3/M/J/02 53 For Examiner’s Use
  55. 55. 3 For Examiner’s Use 2 2. A small rubber ball falls vertically, hits the ground and rebounds vertically upwards. Fig. 2.1 is the speed-time graph for the ball. 10 B speed 8 m/s 6 D 4 2 0 A 0 E C 0.5 1.0 1.5 time / s 2.0 Fig. 2.1 (a) Using information from the graph, describe the following parts of the motion of the ball. (i) part AB ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (ii) part DE ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [3] (b) Explain what is happening to the ball along the part of the graph from B through C to D. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) Whilst the ball is in contact with the ground, what is the (i) overall change in speed, change in speed = ........................................ (ii) overall change in velocity? change in velocity = ...................................... [2] 0625/3/M/J/02 54 [Turn over
  56. 56. 4 (d) Use your answer to (c) to explain the difference between speed and velocity. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (e) Use the graph to calculate the distance travelled by the ball between D and E. distance travelled = ..................................[2] (f) Use the graph to calculate the deceleration of the ball between D and E. deceleration = ..................................[2] 0625/3/M/J/02 55 For Examiner’s Use
  57. 57. 2 1 3. Fig. 1.1 shows apparatus that may be used to compare the strengths of two springs of the same size, but made from different materials. spring scale masses Fig. 1.1 (a) (i) Explain how the masses produce a force to stretch the spring. ................................................................................................................................... (ii) Explain why this force, like all forces, is a vector quantity. ................................................................................................................................... ................................................................................................................................... [2] (b) Fig. 1.2 shows the graphs obtained when the two springs are stretched. force/N 20 spring 1 15 spring 2 10 5 0 0 10 20 30 extension/mm Fig. 1.2 0625/3/M/J/03 56 40 For Examiner’s Use
  58. 58. 3 (i) State which spring is more difficult to extend. Quote values from the graphs to support your answer. For Examiner’s Use ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (ii) On the graph of spring 2, mark a point P at the limit of proportionality. Explain your choice of point P. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (iii) Use the graphs to find the difference in the extensions of the two springs when a force of 15 N is applied to each one. difference in extensions = .................................. [6] 24. The speed of a cyclist reduces uniformly from 2.5 m/s to 1.0 m/s in 12 s. (a) Calculate the deceleration of the cyclist. deceleration = ..................................[3] (b) Calculate the distance travelled by the cyclist in this time. distance = ..................................[2] 0625/3/M/J/03 57 [Turn over
  59. 59. 4 3 5. Fig. 3.1 shows the arm of a crane when it is lifting a heavy box. 1220 N 950 N 40° 30° P box Fig. 3.1 (a) By the use of a scale diagram (not calculation) of the forces acting at P, find the weight of the box. [5] 0625/3/M/J/03 58 For Examiner’s Use
  60. 60. For Examiner’s Use 5 (b) Another box of weight 1500 N is raised vertically by 3.0 m. (i) Calculate the work done on the box. work done = .................................. (ii) The crane takes 2.5 s to raise this box 3.0 m. Calculate the power output of the crane. power = .................................. [4] 4 Fig. 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust particles. syringe seal piston dust particles Fig. 4.1 (a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from 80 cm3 to 25 cm3. Calculate the final pressure of the air. pressure = ..................................[3] 0625/3/M/J/03 59 [Turn over
  61. 61. 2 For Examiner’s Use 6. Fig. 1.1 shows a cycle track. 1 A B E C v = 6 m/s D Fig. 1.1 A cyclist starts at A and follows the path ABCDEB. The speed-time graph is shown in Fig. 1.2. B C D E B 6 speed m/s 5 4 3 2 1 0A 0 10 20 30 40 50 60 70 80 90 100 time / s Fig. 1.2 (a) Use information from Fig. 1.1 and Fig. 1.2 to describe the motion of the cyclist (i) along AB, ................................................................................................................................... (ii) along BCDEB. ................................................................................................................................... ................................................................................................................................... [4] © UCLES 2004 0625/03 M/J/04 60
  62. 62. 3 For Examiner’s Use (b) The velocity v of the cyclist at C is shown in Fig. 1.1. State one similarity and one difference between the velocity at C and the velocity at E. similarity ........................................................................................................................... difference ......................................................................................................................[2] (c) Calculate (i) the distance along the cycle track from A to B, distance = ………………… (ii) the circumference of the circular part of the track. circumference = ………………… [4] © UCLES 2004 0625/03 M/J/04 61 [Turn over
  63. 63. 4 7. Fig. 2.1 shows a rock that is falling from the top of a cliff into the river below. 2 cliff falling rock river Fig. 2.1 (a) The mass of the rock is 75 kg. The acceleration of free fall is 10 m/s2. Calculate the weight of the rock. weight = …………………[1] (b) The rock falls from rest through a distance of 15 m before it hits the water. Calculate its kinetic energy just before hitting the water. Show your working. kinetic energy = …………………[3] (c) The rock hits the water. Suggest what happens to the kinetic energy of the rock during the impact. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] © UCLES 2004 0625/03 M/J/04 62 For Examiner’s Use
  64. 64. 5 For Examiner’s Use 8. A large spring is repeatedly stretched by an athlete to increase the strength of his arms. 3 Fig. 3.1 is a table showing the force required to stretch the spring. extension of spring / m force exerted to produce extension / N 0.096 0.192 0.288 0.384 250 500 750 1000 Fig. 3.1 (a) (i) State Hooke’s law. ................................................................................................................................... ...............................................................................................................................[1] (ii) Use the results in Fig. 3.1 to show that the spring obeys Hooke’s law. [1] (b) Another athlete using a different spring exerts an average force of 400 N to enable her to extend the spring by 0.210 m. (i) Calculate the work done by this athlete in extending the spring once. work done = ………………… (ii) She is able to extend the spring by this amount and to release it 24 times in 60 s. Calculate the power used by this athlete while doing this exercise. power = ………………… [4] © UCLES 2004 0625/03 M/J/04 63 [Turn over
  65. 65. 2 9. A solid plastic sphere falls towards the Earth. 1 Fig. 1.1 is the speed-time graph of the fall up to the point where the sphere hits the Earth’s surface. 140 speed m/s R 120 S T 100 80 60 Q 40 20 0 P 0 10 20 30 40 50 60 70 80 time / s 90 100 110 Fig. 1.1 (a) Describe in detail the motion of the sphere shown by the graph. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [3] © UCLES 2005 0625/03/M/J/05 64 For Examiner’s Use
  66. 66. 3 (b) On Fig. 1.2, draw arrows to show the directions of the forces acting on the sphere when it is at the position shown by point S on the graph. Label your arrows with the names of the forces. [2] Fig. 1.2 (c) Explain why the sphere is moving with constant speed at S. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (d) Use the graph to calculate the approximate distance that the sphere falls (i) between R and T, (ii) between P and Q. distance = ………………. [2] distance = ………………. [2] © UCLES 2005 0625/03/M/J/05 65 [Turn over For Examiner’s Use
  67. 67. 4 10. Fig. 2.1 shows a simple pendulum that swings backwards and forwards between P and Q. 2 support string P R Q pendulum bob Fig. 2.1 (a) The time taken for the pendulum to swing from P to Q is approximately 0.5 s. Describe how you would determine this time as accurately as possible. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) (i) State the two vertical forces acting on the pendulum bob when it is at position R. 1. ............................................................................................................................... 2. .......................................................................................................................... [1] (ii) The pendulum bob moves along the arc of a circle. State the direction of the resultant of the two forces in (i). .............................................................................................................................. [1] (c) The mass of the bob is 0.2 kg. During the swing it moves so that P is 0.05 m higher than R. Calculate the increase in potential energy of the pendulum bob between R and P. potential energy = ………………. [2] © UCLES 2005 0625/03/M/J/05 66 For Examiner’s Use
  68. 68. 5 11. A mass of 3.0 kg accelerates at 2.0 m/s2 in a straight line. 3 (a) State why the velocity and the acceleration are both described as vector quantities. .......................................................................................................................................... ..................................................................................................................................... [1] (b) Calculate the force required to accelerate the mass. force = ………………. [2] (c) The mass hits a wall. The average force exerted on the wall during the impact is 120 N. The area of the mass in contact with the wall at impact is 0.050 m2. Calculate the average pressure that the mass exerts on the wall during the impact. pressure = ………………. [2] © UCLES 2005 0625/03/M/J/05 67 [Turn over For Examiner’s Use
  69. 69. 2 1 12. A bus travels from one bus stop to the next. The journey has three distinct parts. Stated in order they are uniform acceleration from rest for 8.0 s, uniform speed for 12 s, non-uniform deceleration for 5.0 s. Fig. 1.1 shows only the deceleration of the bus. 15 speed m/s 10 5 0 0 5 10 15 time/s 20 25 Fig. 1.1 (a) On Fig. 1.1, complete the graph to show the first two parts of the journey. [3] (b) Calculate the acceleration of the bus 4.0 s after leaving the first bus stop. acceleration = ........................[2] (c) Use the graph to estimate the distance the bus travels between 20 s and 25 s. estimated distance = ........................[2] (d) On leaving the second bus stop, the uniform acceleration of the bus is 1.2 m / s2. The mass of the bus and passengers is 4000 kg. Calculate the accelerating force that acts on the bus. force = ........................[2] (e) The acceleration of the bus from the second bus stop is less than that from the first bus stop. Suggest two reasons for this. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] © UCLES 2006 0625/03/M/J/06 68 For Examiner’s Use
  70. 70. 3 2 13. A student sets up the apparatus shown in Fig. 2.1 in order to find the resultant of the two tensions T1 and T2 acting at P. When the tensions T1, T2 and T3 are balanced, the angles between T1 and the vertical and T2 and the vertical are as marked on Fig. 2.1. pulley pulley T1 = 6.0 N 69° T2 = 8.0 N 44° vertical board P T3 Fig. 2.1 In the space below, draw a scale diagram of the forces T1 and T2. Use the diagram to find the resultant of the two forces. State (a) the scale used, scale = ........................................ (b) the value of the resultant, value = ........................................ (c) the direction of the resultant. © UCLES 2006 direction = ........................................ [6] 0625/03/M/J/06 69 [Turn over For Examiner’s Use
  71. 71. 4 3 14. An electric pump is used to raise water from a well, as shown in Fig. 3.1. pump ground well Fig. 3.1 (a) The pump does work in raising the water. State an equation that could be used to calculate the work done in raising the water. ......................................................................................................................................[2] (b) The water is raised through a vertical distance of 8.0 m. The weight of water raised in 5.0 s is 100 N. (i) Calculate the work done in raising the water in this time. work done = .......................[1] (ii) Calculate the power the pump uses to raise the water. power = ........................[1] (iii) The energy transferred by the pump to the water is greater than your answer to (i). Suggest what the additional energy is used for. ..............................................................................................................................[1] © UCLES 2006 0625/03/M/J/06 70 For Examiner’s Use
  72. 72. Topic 2: Thermal Physics 1 Solids • The particles in solids are tightly held together by strong forces. • They vibrate around mean positions. • The higher the temperature, the more vibrational kinetic energy the particles have. • Solids have a rigid shape. 2 Liquids • In liquids the forces are strong, but the vibrating particles are not fixed in position. • The particles can move but they are held close to their neighbours. • Liquids do not keep their shape. 3 71
  73. 73. Gases • In gases the forces are very weak and they are virtually free to move around their container. • The particles occasionally collide. • Gases expand to fill their container. • The collisions between the particles and the container walls provides pressure. 4 Changing State • When a material changes from one state to another, bonds are either broken or created. • When bonds are broken, heat must be supplied. When bonds are created, heat is released. • When materials change state there is no change in the temperature. 5 Phase Changes • The phase change from solid to liquid is called ‘fusion’. • The phase change from liquid to gas is called ‘vaporisation’. • The energy required to effect the phase change is called the ‘Latent Heat’. • The Latent Heat required per kg is called the ‘Specific Latent Heat’. 6 72
  74. 74. Phases Changes (Graphical) vaporisation Temperature liquid water fusion Time 7 Latent Heat Calculations • The Specific Latent Heat of a material is given the symbol l. • From the definition, we have the following relationship: H = ml H-J m - kg l - J/kg 8 Heat Capacity • Whilst a material is being heated within a certain state of matter, its temperature will rise. • The temperature rise depends upon the mass of the material, the type of material and the amount of heat supplied. • The property of a material that represents how much heat is needed to raise its temperature is called its ‘Specific Heat Capacity’ and is given the symbol c. 9 73
  75. 75. Calculations • To calculate heat required we use: H = mcΔT H-J m - kg C - J/kg/ ºC ∆T - ºC 10 Constant Volume • If we increase the temperature of a gas in a container at a constant volume, the particles will move with more energy, and so there will be more collisions, and so greater pressure: Pressure increases with Temperature 11 Constant Pressure • If we increase the temperature of a gas in a container at a constant pressure, the particles will move with more energy, but they need more space to keep the collisions constant and so there will be a greater volume: Volume increases with Temperature 12 74
  76. 76. Constant Temperature • If we keep the temperature of a gas constant, we keep the kinetic energy of the particles constant. • Decreasing the volume of the gas’ container will increase the number of collisions of the particles with the container. • The pressure of the gas will increase. • Pressure and Volume changes are described by the following relationship: P1V1 = P2V2 13 Brownian Motion • When pollen grains are placed on the surface of a liquid and a strong light source is used to illuminate the pollen, the pollen is seen to move randomly. • This movement is called ‘Brownian Motion’ and cause by the invisible water particles hitting the pollen grains. 14 Expansion • When particles are heated they gain energy. • They become more spaced-out, and the material gets bigger. • We say that the material expands. • Generally, objects expand as they get hotter and contract as they get cooler. • Liquids expand more than solids on heating, and gases expand more than liquids. • Solids expand with the greatest force. Gases expand with the least force. 15 75
  77. 77. Questions on Expansion • Why do walls have expansion joints? • Why are pylon electrical cables tighter in winter? • Why do railway lines leave regular gaps between them? 16 Temperature Scales • The most common temperature scale that is used is the Celsius scale. This has its zero at the freezing point of water, and the boiling point of water is 100°C. • In Physics, the Kelvin scale (or Absolute Temperature scale) is often used. • This is often more sensible as the zero is defined as the point at which the particles have no kinetic energy (Absolute Zero). • To convert between Celsius and Kelvin, we add 273°C. • A rise of 1K is the same as a rise of 1°C. 17 Internal Energy • The Kelvin Temperature is proportional to the average kinetic energy of the particles. 18 76
  78. 78. Evaporation • Evaporation is a process by which a liquid cools due to the fact that particles are lost from its surface. • The higher energy particles will be more likely to leave the liquid, so lowering the average KE of the particles remaining in the liquid. The temperature will thus be lowered. • Increasing the exposed surface area of the liquid, or increasing the movement of air will increase the rate of evaporation. 19 Changing State When a material changes from one state to another, bonds are either broken or created. This involves an associated Internal Energy change. When bonds are broken, heat must be supplied. When bonds are created, Heat is released. Since the energy changes are entirely Internal, there is no change in kinetic energy of the particles, and hence no change in the temperature of the material. 20 Thermometry To make a thermometer, we need a property that changes with temperature in a linear fashion. We then need to calibrate the thermometer by choosing two fixed points. The fixed points for calibration are the boiling point of water (100°C) and the freezing point of water (0°C). The scale is then divided into 100 equal parts for interpolation. 21 77
  79. 79. Liquid in Glass Thermometers • Liquid in glass thermometers have liquid in a glass bulb. As the liquid is heated it expands and its level rises up the scale. • The choice of liquid, the thinness of the bore or the size of the bulb will affect the sensitivity of the thermometer. • The choice of liquid will affect the range of the thermometer. 22 Thermocouple • A thermocouple is a junction of two different metals. • Electrons will move across the junction creating a measurable voltage. • The higher the temperature, the more energy the electrons will have, more electrons will move and we get a greater voltage. • The voltage is then calibrated. • High temperatures can be quickly recorded. 23 Heat Transfer • Heat flows from hot areas to cold areas. • In solids, heat moves by conduction. • In liquids and gases (fluids), heat moves by convection. • In a vacuum heat has to move by radiation. 24 78
  80. 80. Conduction Heat Heat • Heat moves from particle to particle as they collide. • Poor conductors are called insulators. • Solids are the best conductors (especially metals). • Gases are the best insulators. 25 Questions on Conduction. 1. Why does a robin fluff up its feathers in Winter? 2. Why is a string vest warmer than a cotton vest? 3. Design an experiment to compare conductors. 26 Convection Cool fluid in a beaker. Convection currents circulate the heat. Heat source is applied. Warm fluid expands and rises. (low density) Denser Cool fluid sinks Heat 27 79
  81. 81. Questions on Convection • Why should you stay close to the ground in a smokefilled room? • Why is the heating element at the bottom of a kettle? 28 Radiation Hot object (warmer than surroundings). Infra-red light energy emitted.. Cooler object 29 Radiation • Black objects are better radiators and absorbers than white or shiny objects. • Rough objects are better radiators and absorbers than shiny or smooth objects. 30 80
  82. 82. Questions on Radiation • Why are houses often painted white in hot countries? • Why do marathon runners wear an aluminium blanket at the end of a race? 31 The Vacuum Flask stopper silver surface vacuum 32 81
  83. 83. 1 Thermal Physics Quantity and symbol Symbol equation Definition The temperature of a gas is related to the motion of its particles. The faster, and Temperature, T, θ therefore the more energetic the particles the hotter the gas. The random, jerky motion of particles (pollen in water, smoke in air) in a Brownian Motion suspension is evidence for the kinetic model of matter. The massive particles are moved by light, fast moving molecules. The more energetic molecules escape from the surface of a liquid. This leaves the Evaporation liquid left behind with a lower average KE, and hence a cooler liquid. For a fixed mass of gas, the pressure is Pα1 inversely proportional to the volume, (at V Boyles’ Law constant temperature) PV = k For a fixed mass of gas, the volume is VαT Charles’ Law directly proportional to the temperature, (at V=kT constant pressure) For a fixed mass of gas, the pressure is PαT directly proportional to the temperature, (at P=kT Pressure Law constant volume) For a fixed mass of gas, the PV = k Pressure x Volume = a constant T Gas Law Temperature P1V1 = P2V2 T1 T2 The amount of heat energy required to c=E Thermal Capacity, c change the temperature of a body by 1 oC ΔT The amount of heat energy required to c=Q Specific Heat change the temperature of a unit mass of a mΔT Capacity, c o substance by 1 C The amount of energy required to change Latent Heat, L the state of a body without a change in temperature The amount of energy required to change L=Q Specific Latent Heat the state of unit mass of substance, from m of Fusion, L solid to liquid without a change in temperature The amount of energy required to change L=Q Specific Latent Heat the state of unit mass of a substance from m of Vaporisation, L liquid to gas without a change in temperature The movement of heat energy by the passing on of vibrations from particle to Conduction particle. 82 units o C, K Temperature must be the absolute temperature in Kelvin, K. The other quantities must be consistent. J/ oC J/kg oC Jkg oC J J/kg J/g J/kg J/g
  84. 84. 2 Convection Radiation The movement of heat energy by the mass movement of fluids, due to expansion and density changes due to heating. The movement of heat energy by the form of an electromagnetic wave. (Infrared) 83
  85. 85. iGCSE Physics Past Paper Questions Paper 1 Compilation Thermal Physics 84
  86. 86. 7 1. 14 The diagram represents molecules in a liquid. A and C are molecules with a high amount of energy. B and D are molecules with a low amount of energy. Which molecule is most likely to be leaving the liquid by evaporation? A B D C 15 The size of a balloon increases when the pressure inside it increases. 2. The balloon gets bigger when it is left in the heat from the Sun. cool balloon hot balloon Why does this happen? A The air molecules inside the balloon all move outwards when it is heated. B The air molecules inside the balloon are bigger when it is heated. C The air molecules inside the balloon move more quickly when it is heated. D The number of air molecules inside the balloon increases when it is heated. 3. 16 What must expand in order to show the temperature rise in a mercury-in-glass thermometer? A the glass bulb B the glass stem C the mercury D the vacuum 0625/1/M/J/02 85 [Turn over
  87. 87. 8 4. 17 The table shows the melting points and boiling points of four substances. Which substance is a liquid at a room temperature of 20 oC? substance melting point / oC boiling point / oC A –101 –35 B –39 357 C 30 2100 D 327 1750 18 A bar made of half wood and half copper has a piece of paper wrapped tightly round it. 5. The bar is heated strongly at the centre for a short time, and the paper goes brown on one side only. wood paper copper heat Which side goes brown, and what does this show about wood and copper? brown side wood copper A copper conductor insulator B copper insulator conductor C wood conductor insulator D wood insulator conductor 0625/1/M/J/02 86
  88. 88. 9 6. 19 The diagrams show part of a water-heating system which is working by convection. Which diagram shows the most likely flow of water in the system? A B hot water tank hot water tank boiler boiler heat heat C D hot water tank hot water tank boiler boiler heat 9 heat 19 The diagram shows a heater used to heat a tank of cold water. 7. 20 A drop of water from a tap falls onto the surface of some water of constant depth. water lagging view from above tank heater Water waves spread out on the surface of the water. Which statement is true? A What is the main process and travel at the same speed in all directions. The waves are longitudinal by which heat moves through the water? B The waves are longitudinal and travel more quickly in one direction than in others. A conduction C The waves are transverse and travel at the same speed in all directions. B convection D The waves are transverse and travel more quickly in one direction than in others. C evaporation D radiation 0625/1/M/J/02 20 What causes refraction when light travels from air into glass? A 87 The amplitude of the light waves changes. [Turn over
  89. 89. 7 15 Two metal boxes containing air are standing in a room. Box X is on top of a heater. Box Y is on a 8. bench. The boxes are left for a long time. Y X heater bench Which line in the table best describes the average speed of the molecules in the containers? box X box Y A fast zero B fast slow C slow fast D zero fast 9. 16 The top of the mercury thread in a mercury-in-glass thermometer reaches point X at 0 °C and point Z at 100 °C. Z Y X W Where might it be at a temperature below the ice-point? A point W B point X C point Y D point Z 0625/01/M/J/03 88 [Turn over
  90. 90. 8 17 The same quantity of heat energy is applied to four different blocks. The temperature rise 10. produced is shown on each block. Which block has the highest thermal capacity? A B temperature rise is 3 °C temperature rise is 6 °C C D temperature rise is 18 °C temperature rise is 9 °C 11. 18 A person holds a glass beaker in one hand and fills it quickly with hot water. It takes several seconds before his hand starts to feel the heat. Why is there this delay? A Glass is a poor conductor of heat. B Glass is a good conductor of heat. C Water is a poor conductor of heat. D Water is a good conductor of heat. 0625/01/M/J/03 89
  91. 91. 7 14 A student places his thumb firmly on the outlet of a bicycle pump, to stop the air coming out. trapped air direction of motion handle What happens to the pressure and to the volume of the trapped air as the pump handle is pushed in? pressure volume A decreases decreases B decreases remains the same C increases decreases D increases remains the same 15 A balloon is inflated in a cold room. When the room becomes much warmer, the balloon becomes larger. How does the behaviour of the air molecules in the balloon explain this? A The molecules become larger. B The molecules evaporate. C The molecules move more quickly. D The molecules repel each other. 9 19 The diagram shows a block of ice placed in a warm room. At which point is the temperature the lowest? $ D ! &$"'( )&% !"#$% C " B # A 20 The drawing shows a wave. Which labelled distance is the wavelength? © UCLES 2004 0625/01/M/J/04 90 A [Turn over
  92. 92. 8 12. 16 A substance is heated at a steady rate. It changes from a solid to a liquid, and then to a gas. The graph shows how its temperature changes with time. S temperature 5 R Q 11 The diagram shows a thick sheet of glass. Which edge must it stand on to cause the greatest pressure? P A time B Which parts of the graph show a change of state taking place? A P and R B P and S C Q and R D Q and S D C 13. An engineer wants to fix a steel washer on to a steel rod. The rod is just too big to fit into the hole 17 12 A manometer is being used to measure the pressure of the gas inside a tank. A, B, C and D of the washer. show the manometer at different times. steel steel rod At which time is washer pressure inside the tank greatest? the gas A B C How can the engineer fit the washer onto the rod? gas A cool the washer and put it over the rod B cool the washer and rod to the same temperature and push them together C heat the rod and then place it in the hole D heat the washer and place it over the rod 13 Brownian motion is seen by looking at smoke particles through a microscope. 14. How do the smoke particles move in Brownian motion? A all in the same direction B at random C in circles D vibrating about fixed points © U C L E S 2004 0625/01/M/J/04 91 D
  93. 93. 9 15. 18 An experiment is set up to find out which metal is the best conductor of heat. Balls are stuck with wax to rods made from different metals, as shown in diagram X. The rods are heated at one end. Some of the balls fall off, leaving some as shown in diagram Y. Which labelled metal is the best conductor of heat? diagram X diagram Y A h e a t B h before heating C e a D t after heating 16. Thermometer X is held above an ice cube and thermometer Y is held the same distance below 19 the ice cube. After several minutes, the reading on one thermometer changes. The ice cube does not melt. thermometer X ice cube thermometer Y Which thermometer reading changes and why? thermometer reason A X cool air rises from the ice cube B X warm air rises from the ice cube C Y cool air falls from the ice cube D Y warm air falls from the ice cube UCLES 2004 0625/01/M/J/04 92 [Turn over
  94. 94. 7 17. 14 Viewed through a microscope, very small particles can be seen moving with Brownian motion. Which line in the table is correct? type of motion of particles particles are suspended in A vibration a liquid or a gas B vibration a solid, a liquid or a gas C random a liquid or a gas D random a solid, a liquid or a gas 15 18. A measured mass of gas is placed in a cylinder at atmospheric pressure and is then slowly compressed. piston gas piston pushed in The temperature of the gas does not change. What happens to the pressure of the gas? A It drops to zero. B It decreases, but not to zero. C It stays the same. D It increases. 16 The graph shows the change in temperature of a material as it is heated. 19. Which part on the graph shows when the material is boiling? D temperature C B A time © UCLES 2005 0625/01/M/J/05 93 [Turn over
  95. 95. 8 20. 17 An experiment is set up as shown. pressure gauge air flask water heat What does the pressure gauge show as the air in the flask becomes hotter? A a steady pressure B a decrease in pressure C an increase in pressure D an increase and then a decrease in pressure 18 An iron bar is held with one end in a fire. The other end soon becomes too hot to hold. hand fire iron bar 21. How has the heat travelled along the iron bar? A by conduction B by convection C by expansion D by radiation © UCLES 2005 0625/01/M/J/05 94
  96. 96. 6 22. 14 Driving a car raises the temperature of the tyres. This causes the pressure of the air in the tyres to increase. Why is this? A Air molecules break up to form separate atoms. B Air molecules expand with the rise in temperature. C The force between the air molecules increases. D The speed of the air molecules increases. 23. To mark a temperature scale on a thermometer, fixed points are needed. 15 Which is a fixed point? A the bottom end of the thermometer tube B the top end of the thermometer tube C the temperature of pure melting ice D the temperature of pure warm water 24. 16 Four blocks, made of different materials, are each given the same quantity of internal (heat) energy. Which block has the greatest thermal capacity? A C D temperature rise = 2 oC © UCLES 2006 B temperature rise = 4 oC temperature rise = 6 oC temperature rise = 8 oC 0625/01/M/J/06 95
  97. 97. 7 25. 17 A long thin bar of copper is heated evenly along its length. copper bar heat What happens to the bar? A It becomes lighter. B It becomes longer. C It becomes shorter. D It bends at the ends. 18 A beaker contains water at room temperature. water X Y 26. How could a convection current be set up in the water? A cool the water at X B cool the water at Y C stir the water at X D stir the water at Y 8 19 Two plastic cups are placed one inside the other. Hot water is poured into the inner cup and a lid is put on top as shown. lid small spacer small air gap hot water bench 27. Which statement is correct? A Heat loss by radiation is prevented by the small air gap. B No heat passes through the sides of either cup. C The bench is heated by convection from the bottom of the outer cup. D The lid is used to reduce heat loss by convection. © UCLES 2006 0625/01/M/J/06 96 20 Which is the best description of the speed of a water wave? [Turn over
  98. 98. iGCSE Physics Past Paper Questions Paper 3 Compilation Thermal Physics 97
  99. 99. 5 3 1. Fig. 3.1 is an attempt to show the molecules in water and the water vapour molecules over the water surface. For Examiner’s Use water vapour molecules water molecules Fig. 3.1 (a) Explain, in terms of the energies of the molecules, why only a few water molecules have escaped from the water surface. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) State two ways of increasing the number of water molecules escaping from the surface. 1 ....................................................................................................................................... 2 .................................................................................................................................. [2] (c) Energy is required to evaporate water. Explain, in molecular terms, why this energy is needed. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] 0625/3/M/J/02 98 [Turn over
  100. 100. 6 42. (a) Fig. 4.1 shows a cylinder containing air at a pressure of 1.0 × 105 Pa. The length of the air column in the cylinder is 80 mm. 80 mm air piston cylinder Fig. 4.1 The piston is pushed in until the pressure in the cylinder rises to 3.8 × 105 Pa. Calculate the new length of the air column in the cylinder, assuming that the temperature of the air has not changed. new length = .................................. [3] (b) Fig. 4.2 shows the same cylinder containing air. air Fig. 4.2 The volume of the air in the cylinder changes as the temperature of the air changes. (i) The apparatus is to be used as a thermometer. Describe how two fixed points, 0 °C and 100 °C, and a temperature scale could be marked on the apparatus. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (ii) Describe how this apparatus could be used to indicate the temperature of a large beaker of water. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [5] 0625/3/M/J/02 99 For Examiner’s Use
  101. 101. [4] 4 Fig. 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust 5 particles. 3. (b) Another box of weight 1500 N is raised vertically by 3.0 m. (i) syringe Calculate the work done on the box. seal piston work done = .................................. dust particles (ii) For Examiner’s Use The crane takes 2.5 s to raise this box 3.0 m. Calculate the power output of the Fig. 4.1 crane. (a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... power = .................................. [4] .......................................................................................................................................... 4 ......................................................................................................................................[3] Fig. 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust particles. (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from syringe 80 cm3 to 25 cm3. Calculate the final pressure of the air. seal piston pressure = ..................................[3] dust particles 0625/3/M/J/03 Fig. 4.1 [Turn over (a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from 80 cm3 to 25 cm3. Calculate the final pressure of the air. pressure = ..................................[3] 0625/3/M/J/03 100 [Turn over
  102. 102. 6 54. Fig. 5.1 shows a thermocouple set up to measure the temperature at a point on a solar panel. Sun's rays surface of solar panel Z X cold junction Y hot junction Fig. 5.1 (a) X is a copper wire. (i) Suggest a material for Y. ................................................................................................................................... (ii) Name the component Z. ................................................................................................................................... [2] (b) Explain how a thermocouple is used to measure temperature. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (c) Experiment shows that the temperature of the surface depends upon the type of surface used. Describe the nature of the surface that will cause the temperature to rise most. .......................................................................................................................................... ......................................................................................................................................[1] 0625/3/M/J/03 101 For Examiner’s Use
  103. 103. 6 5. (a) Two identical open boxes originally contain the same volume of water. 4 One is kept at 15 °C and the other at 85 °C for the same length of time. Fig. 4.1 shows the final water levels. 15 °C 85 °C Fig. 4.1 With reference to the energies of the water molecules, explain why the levels are different. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) In an experiment to find the specific latent heat of vaporisation of water, it took 34 500 J of energy to evaporate 15 g of water that was originally at 100 °C. A second experiment showed that 600 J of energy was lost to the atmosphere from the apparatus during the time it took to evaporate 15 g of water. Calculate the specific latent heat of vaporisation of water that would be obtained from this experiment. specific latent heat = …………………[3] © UCLES 2004 0625/03 M/J/04 102 For Examiner’s Use
  104. 104. 7 56. (a) Fig. 5.1 shows two identical metal plates. The front surface of one is dull black and the front surface of the other is shiny silver. The plates are fitted with heaters that keep the surfaces of the plates at the same temperature. dull black For Examiner’s Use shiny silver Fig. 5.1 (i) State the additional apparatus needed to test which surface is the best emitter of heat radiation. ................................................................................................................................... (ii) State one precaution that is needed to ensure a fair comparison. ................................................................................................................................... ................................................................................................................................... (iii) State the result that you expect. ................................................................................................................................... (iv) Write down another name for heat radiation. ................................................................................................................................... [4] (b) In the space below, draw a labelled diagram of an everyday situation in which a convection current occurs. Mark the path of the current with a line and show its direction with arrows. © UCLES 2004 0625/03 M/J/04 103 [3] [Turn over
  105. 105. 6 7. 4 Fig. 4.1 shows apparatus that a student uses to make an estimate of the specific heat capacity of iron. electrical heater thermometer iron block Fig. 4.1 (a) The power of the heater is known. State the four readings the student must take to find the specific heat capacity of iron. 1. ...................................................................................................................................... 2. ...................................................................................................................................... 3. ...................................................................................................................................... 4. ................................................................................................................................. [3] (b) Write down an equation, in words or in symbols, that could be used to work out the specific heat capacity of iron from the readings in (a). [2] © UCLES 2005 0625/03/M/J/05 104 For Examiner’s Use
  106. 106. 7 (c) (i) Explain why the value obtained with this apparatus is higher than the actual value. ................................................................................................................................... .............................................................................................................................. [1] (ii) State one addition to the apparatus that would help to improve the accuracy of the value obtained. ................................................................................................................................... .............................................................................................................................. [1] © UCLES 2005 0625/03/M/J/05 105 [Turn over For Examiner’s Use
  107. 107. 8 5 8. (a) Fig. 5.1 shows the paths of a few air molecules and a single dust particle. The actual air molecules are too small to show on the diagram. paths of air molecules dust particle Fig. 5.1 Explain why the dust particle undergoes small random movements. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [4] (b) Fig. 5.2 shows the paths of a few molecules leaving the surface of a liquid. The liquid is below its boiling point. air and vapour liquid Fig. 5.2 (i) State which liquid molecules are most likely to leave the surface. ................................................................................................................................... .............................................................................................................................. [1] (ii) Explain your answer to (i). ................................................................................................................................... ................................................................................................................................... .............................................................................................................................. [2] © UCLES 2005 0625/03/M/J/05 106 For Examiner’s Use
  108. 108. 5 4 9. (a) State two differences between evaporation of water and boiling of water. 1. ...................................................................................................................................... 2. ..................................................................................................................................[2] (b) The specific latent heat of vaporisation of water is 2260 kJ / kg. Explain why this energy is needed to boil water and why the temperature of the water does not change during the boiling. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (c) A laboratory determination of the specific latent heat of vaporisation of water uses a 120 W heater to keep water boiling at its boiling point. Water is turned into steam at the rate of 0.050 g / s. Calculate the value of the specific latent heat of vaporisation obtained from this experiment. Show your working. specific latent heat of vaporisation = ........................[3] © UCLES 2006 0625/03/M/J/06 107 [Turn over For Examiner’s Use
  109. 109. 6 510. (a) Fig. 5.1 shows a tank used for evaporating salt solution to produce crystals. evaporating tank steam in salt solution steam out Fig. 5.1 Suggest two ways of increasing the rate of evaporation of the water from the solution. Changes may be made to the apparatus, but the rate of steam supply must stay constant. You may assume the temperature of the salt solution remains constant. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] (b) A manufacturer of liquid-in-glass thermometers changes the design in order to meet new requirements. Describe the changes that could be made to (i) give the thermometer a greater range, ..............................................................................................................................[1] (ii) make the thermometer more sensitive. ..............................................................................................................................[1] (c) A toilet flush is operated by the compression of air. The air inside the flush has a pressure of 1.0 × 105 Pa and a volume of 150 cm3. When the flush is operated the volume is reduced to 50 cm3. The temperature of the air remains constant during this process. Calculate the new pressure of the air inside the flush. pressure = .......................[2] © UCLES 2006 0625/03/M/J/06 108 For Examiner’s Use
  110. 110. Topic 3: Waves 1 Transverse Waves Wavelength amplitude amplitude Wavelength Frequency=Number of Waves per second (Hz) 2 Types of Waves • Waves carry energy without matter being transferred. • There are two types of wave motion: • Transverse. • Longitudinal. 3 109
  111. 111. Transverse Waves • In a transverse wave, the wave motion is at right angles to the direction of the wave. • The Energy flows in a direction at right angles to the wave motion. • Examples of transverse waves are Light, Pond-ripples, Seismic Swaves. 4 Longitudinal Waves  In a longitudinal wave, the wave motion is along the direction of the wave. It consists of a series of compressions and rarefractions.  The Energy flows in the same direction as the wave motion.  Examples of longitudinal waves are Sound and Seismic P-waves. 5 Reflection • If waves hit a boundary, they will reflect. • The angle of incidence will be equal to the angle of reflection. Incident wavefronts Reflected wavefronts Reflecting Surface Normal 6 110
  112. 112. Refraction • If a wave changes speed, its direction will change. • If it slows-down it will bend towards the normal. • If the wave speeds-up it will bend away from the normal. Incident wavefronts Boundary Refracted Wavefronts Normal 7 Diffraction • If a wave encounters a gap that is of a similar size as the wavelength of the wave, we will get diffraction. • The wave appears to spread-out from the gap. 8 Period of a Wave • The period of a wave is the time taken for the wave to complete one cycle. • There is a simple relationship between Period (T) and Frequency (f): Period = 1 frequency 9 111

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