1) Light refracts when passing from one medium to another of different density, bending towards the normal. The refractive index is a ratio of light speeds and relates the angle of incidence to refraction. 2) Total internal reflection occurs at a critical angle when light passes from a dense to less dense medium. 3) A prism disperses white light into a spectrum due to different refractive indices for each color, with violet refracting most and red least.

1. Written by MJ Bradley
P5 SPACE FOR REFLECTION incident ray
i i-angle of incidence
air
Refraction
The critical angle 1
glass refracted ray When light passes 2
Light refracts (bends) when it enters a substance of differ- form a more dense
ent density because it changes speed. Refractive index is substance to a less glass
a measure of how much a substance bends light r r-angle of refraction dense substance
there is a critical 2
Calculating refractive index (n):n = light speed in vacuum n = sin i angle (c) where the 1 c
Dispersion of emerging ray
light speed in substance sin r Light In a grazes the bound- At angles of incidence
prism light is ary surface greater than the critical
Question : What is the refractive index of glass for light at an incident angle dispersed into angle TIR occurs
of 30o which refracts with an angle of refraction equal to 20o? different col-
ours because The Endoscope
Answer: n = sin i/sinr = sin30/sin20 = 0.5/0.34 = 1.47 each colour (or
frequency) is In an endoscope some opti-
refracted differ- cal fibres totally internally
How Optical Fibre works ently
Total Internal Reflection reflect light down towards
less dense layer the stomach (in this exam-
cats-eye. Light is ple) and other optical fibres
i internally reflected inside dense
the glass prism i take the reflected light from
Violet is the stomach back to be
TIR occurs when the refracted the
incident ray is at an angle, i, most and red viewed by a camera and
greater than the critical The light totally internally reflects at the the least screen
angle inside a dense boundary of the two layers. i must be
material greater than the critical angle Convex lens: these refract light rays inwards
Optical fibre and Communications
Digital signals (on and off) can be transmitted using
Fibre optic cable optical fibre. Infra-red pulses in digital code are
totally internally reflected along the fibre principal axis C f
Light is internally reflected
down the cable. Endoscopes Diffraction: This is the spread- f
use fibre optic cable The fatter the
ing out of waves when they pass lens the shorter
through a gap or pass an object. the focal length
Wave revision: The effect is greatest when the
The greater wavelength equal the gap width
the ampli- Principal focus: rays parallel to the principal
wavelength
amplitude tude the
brighter axis are refracted towards the principal focus (f).
the light The distance cf is the lens FOCAL LENGTH
or the
louder the Images from a convex lens
sound Rule1: A ray parallel to the principal axis is refracted
through the principal focus F
Interference: Waves can interfere with each other constructively Rule 2: A ray through the optical centre does not change
direction.
(add) or destructively (cancel each other out)
peaks and The peaks of tree lens
troughs one wave add F F
match to the troughs
of the other 2F image of tree
the image is upside
down and smaller,It is a
REAL image - it can be
destructive interference projected onto a screen
constructive interference tree
An Interference Experiment F F
The sound from B quiet
2F the image is
Waves can interfere with each other has travelled 1/2 a u p s i d e
to produce patterns as shown exam- wavelength further loud down and is
ples are light, sound and microwaves than from A. Peaks magnified
match with troughs quiet The image is now
and destructive inter- the correct way up It is a real
ference occurs loud and magnified. The image
A eye traces back
quiet The sound from A where the rays
loudspeaker and B has travelled seem to have come A magnifying glass!
loud the same distance. from. It is not a real
loudspeaker Peaks match with image we call it a
quiet peaks and con- virtual image
Other loud areas are heard structive interfer- 2F F F
because the path differ- loud ence occurs
B ence between the two Magnification
waves is a whole number quiet
of wavelengths. Peaks magnification = height of image
match with peaks and con-
structive interference oc- loud height of object
curs. Why are other quiet A lens Camera
quiet eye
lens
Projector
film - not digital!
convex lens
bulb
tree
The lens can move forwards or backwards The lens is moved in
screen
to make a sharp focus. The closer the ob- or out to focus the
ject the further the lens must be pulled image on the screen
outwards slide

2. Displacement(s) and Velocity(v) Acceleration
Scalar and Vector Quantities Displacement is distance in a given direction. acceleration = velocity change, a = v-u v-u
Velocity = displacement (m) v = s/t (m/s2) time (s) t a t
A scalar quantity has only size.
(m/s) time (s) v = final velocity, u = initial velocity, t = time
A vector has size and direction
Vector addition Example what is the acceleration of a car if
scalar vector it accelerates from 10m/s to 20m/s in 2s?
1)Vectors in the same direction add
distance displacement 2) Vectors in opposite directions subtract u=10m/s, v=20m/s, t =2s, a=?
2
3) For vectors at right angles use pythagorous a = (v-u)/t = (20-10)/2 =10/2 = 5m/s
speed velocity theorem to work out the resultant
temperature force 10N 10N √(10 2 +10 2 )= Equations of Motion for an Object with
10N √200=14.3Ν constant acceleration
10N
mass acceleration 10N
resultant = 10-10
resultant = 10+10 10N
v = u + at
= 0N 1) Write down data
energy momentum = 20N 10N 10N v2 = u2 + 2as
2) Select the appropriate
s = ut + 1/2at2 equation
Momentum: Objects with large mass and velocity have a big momentum
momentum = mass x velocity Example: A rocket accelerates at 1000m/s2 for
p 20s. What distance is travelled?
(kgm/s) ( kg) (m/s)
m v a = 1000m/s2, t = 20s, s=?
p = mv
s = ut + 1/2at2 = 1000x20 + 0.5x1000x202
Example: What is the momentum of a 200000kg train travelling at 20m/s?
= 20000 +200000 = 220000m
Answer: p = mv = 200000x20 = 4000000kgm/s
Force and Momentum:When momentum changes there is a resultant Projectiles: An object fired horizontally will
force. The bigger the rate of change of momentum the bigger the force move at steady speed horizontally (ignoring
air resistance) but will accelerate downwards
F = rate of change of momentum Force in collisions. To reduce the force because of gravity
F(N) = mv - mu (same as F = ma) momentum needs to reduce more slowly
i.e. make the time for collision longer using vh vh
t(s) vh
crumple zones or airbags
vv vv
vv vh
Momentum and collisions: Momentum before = momentum after. This is a very important physics law
Projectiles take a
parabolic shape through
the air vh
Example A 1000kg car travelling at 20m/s hits a stationary 20000kg lorry. (a) What is the vv
momentum of the car before impact? Answer :Momentum before = mbvb=1000x20 = 20000kgm/s
To answer questions about projectiles
(b)If they stick together what is their velocity after the impact? vv
use v h=s h/t for the horizontal motion
Answer: Momentum before = momentum after so mbvb = mava (steady velocity horizontally)
20000 = (1000+20000)Va Use sd = udt + 1/2at2 or vd2 = ud2 + 2asd for
20000 = 21000Va so Va = 20000/21000 = 0.8m/s the downwards motion
Newtons III Law When walking your foot pushes back on the road and the road pushes with an equal and
When two bodies interact opposite forwards force which causes you to accelerate forwards. The Earth beneath you
they exert equal and oppo- also accelerates backwards but you do not notice it because the Earth is so massive
site forces on each other
Microwave and Radiowave Communications Satellites
Microwave Microwave communications must Man made satellites
be in line of sight. Microwaves are Medium wave- i on
can be used for com-
satellite transmitted to a satellite and are re- lengths (around osp
her
munications,
receiver satellite transmitted back to another location 300m) reflect from e weather forecasting,
the ionosphere) defence, surveying.
transmitter on the Earth. Medium radio wave-
ground lengths are reflected from the iono- Geostationary
station sphere back to the Earth's surface. Orbits
transmitter This however is unpredictable and
is affected by the sun. Long wave- Satellites near to the
lengths can be diffracted around the earth orbit quickly
Earth's surface. Microwaves Long wave radio because gravity is
(wavelength (wavelengths strong.
ground station around 1m) 1km) will diffract
receiver must be in line At a certain distance
of sight around the satellites orbit at the
Earth's surface
same rate as the
Diffraction and communications Earth spins and seem
Diffraction is the bending of stationary in the sky.
waves around obstacles or cor- Satellite Orbits and Centripetal Force They are in a
ners. In radio communications geostationary orbit -
longer wavelengths diffract the very useful for
most. This house will not receive Diffraction can cause some communications
short wavelength signals because signal loss at the edge of the F
they do not diffract around the hill transmission dish
earth
comets are natural satellites of the sun as A satellite would rather travel in a straight line if it could!
they approach the sun they accelerate be- Gravity is the centripetal(central) force, F which pulls them
sun cause gravity is stronger. The tail forms
because the icy surface evaporates round in an ellipse shape we call an orbit The moon orbits the
earth in the same way and the Earth around the Sun

3. FOLD ALONG LINE WRITTEN BY MJ BRADLEY
Revision Exercise Unit P5
1) slows
1) When light passes into a more dense substance it ________ down 2) n = sin i n = speed of light in vacuum
2) Two equations for refractive index are.......................... sin r speed of light in substance
3) Label this diagram with i for the angle of air
i
incidence, r for the angle of refraction air
glass glass
3b) Light enters the glass at an angle of incidence equal to 30o. The n = sin i = sin 30 = 0.5 = r
angle of refraction is 20o. What is the refractive index of the glass? sin r sin 20
4) Total internal reflection can only occur at a ________ dense to _____ 4) more, less, critical
dense boundary and when the angle of incidence is greater than the
_________ angle
5) refraction, least, violet
5) White light shone into a glass prism is dispersed into different colours
because the amount of ________ is different for each colour. Red is
refracted the _______ and ________ the most.
6) Complete the paths of these light rays as 6)+6b)
they emerge from a convex lens
F
6b) Label the principle focus F
7) Draw two rays from the top of the tree and
show where its image will be formed 7 lens
lens
F F
tree
F F 2F
2F
7b) Describe how the image is different to the object 7b) upside down and smaller
8) Draw two rays from the top of the pencil and show where its image
will be formed 8) pencil
F
pencil
2F
F F
F
2F
9) Trace back the paths of these rays and show where the top of the 9)+9b) magnifying glass
pencil image will seem to be
9b) What type of optical instrument could this be?
2F F F
9c) Magnification = ?/?
9c) = image height
2F F F object height
10) In a camera and projector how is the image focused? 10) By moving the convex lens in or out
11) Constructive interference between two waves occurs 11) peaks match with peaks
when......................................... eye
12) Destructive interference between two waves occurs
when......................................... eye 12) peaks match with troughs
13) If the path difference between two waves is a whole 13) constructive
number of wavelengths _________ interference will occur
14) If the path difference between two waves is any 14) destructive
number of half wavelengths _________ interference oc-
curs
15)Write the following data down using the correct symbols: t, v, u, S, a 15) t = 5s, v = 30m/s, u = 20m/s, S = 125m, a = 2m/s2
A car travelling at 20 m/s accelerates to 30m/s in 5s. The acceleration of the
car is 2m/s2 and the displacement is 125m
16) A man walks 100m east then 25m 16a) d = 100 + 25 = 125m
north 25m
start
(a) What is the total distance walked?
(b) What is the displacement from the 100m (b) displacement S = √(1002 + 252) =
start?
17) All vector quantities have size and _______________ 17) direction
18) Scaler quantities have _________ only 18) size
19) A stone is dropped from rest and falls for 3s. Use s =ut + at2/2 to find 19) s =ut + at2/2 = 0x3 + 10x32/2
out how far it will fall in 3s (Acceleration due to gravity = 10m/s2) = 0 + 10x9/2 = 45m

4. WRITTEN BY MJ BRADLEY
Revision Exercise Unit P5 FOLD ALONG LINE
20)
20) A stone is thrown horizontally with a velocity of 20m/s at a height of 1.5m
(a) parabolic
(a) What shape describes the path the stone will take
(b) constant
(b) What can you say about the horizontal velocity of the stone?
(c) zero
(c) What is the initial velocity vertically?
(d) s =ut + at2/2
(d) Use s =ut + at2/2 to work out the time it takes for the stone to hit the
ground (acceleration due to gravity = 10m/s2) 1.5=0xt+10t2/2 = 5t2 so t2 = √(1.5/5) =
(e) How far will the stone travel horizontally before hitting the ground?
21) A car must stop form a speed of 50 m/s in 20m, what is the deceleration? 21) s = v2 - u2 = 02-502 = 0 - 2500 = -2500 = -25 m/s2
(Clue use v2=u2 + 2as)
2s 2x50 100 100
22) Momentum = ___________ x ____________ or P =mv 22) mass x velocity
23) The unit of mass is kg, the unit of velocity is _____, the unit of momentum is 23) m/s, kgm/s
_________
24) The momentum before a collision = ________________________
24) momentum after collision
25) What is the momentum of a 1000Kg car travelling at 10m/s? 25) p = mv = 1000x10 = 10000kgm/s
25b) The car collides with a stationary 10000kg bus and they stick together. What 25b) 10000kgm/s
must be their combined momentum after the collision?
b(ii) 10000 = (10000+1000)v
b(ii) What velocity do they have?
so 11000v = 10000 v = 10000/11000 v=
26) In a collision the forces are large if momentum changes very ________ 26) quickly
27) force = change in momentum, in symbols F = ? - ? 27) change in momentum, in symbols F = mv - mu
? ? time t
28) A 1000kg car has a velocity of 50m/s. It hits a bridge and stops in 0.5s. 28)
(i) What is the momentum before hitting the bridge? (i) P = mu = 1000 x 50 = 50000 kgm/s
(ii) What is the momentum of the car only after the collision? (ii) P = mv = 1000 x 0 = 0
(iii) What is the change in momentum? (iii) change = mv - mu = -50000kgm/s
(iv) What is the force? (iv) F = (mv-mu)/t = -50000/0.5 = 100000N
(v) How can the force on the car be reduced? Explain why (v) Use crumple zones - they increase the time for
collision
28b) When the car hit the bridge the force of the car on the 28b) car
bridge was equal and opposite to the force of the bridge on
the............................................
29) Diffraction is the ______ of waves obstruction 29) bending, gap, wavelength
as they pass through a ______. The
effect is greatest when the gap width is
equal to the ___________. Wider gaps
cause little bending
wave crests
large gap
30) Explain why this house can receive long 30) Longer wavelengths are able to diffract around the
wave radio but not short wave radio mountain
31) In radio communications long waves are able to ____ around the
earths' surface. Medium waves are able to reflect off the ________. 31) diffract, ionosphere, sight, Earth
Micro waves work only by line of _______ and need satellites to
relay signals around the ______.
32) Three uses of satellites are ................................... 32) communications, defence, weather forecasting
33) Satellites are kept in orbits by the Earths _______. This is an 33) gravity, centripetal, straight
example of a ________ force and without it satellites would continue
in a ________ line away from the Earth
34) A satellite in a geostationary orbit moves at the same rate as the 34) spins on its axis
Earth _______. 35) natural, gravity gets stronger
35) Comets are _________ satellites of the Sun. As they approach the
Sun they speed up because...........

5. PHYSICS ASSESSMENT P5
SPACE FOR REFLECTION
Name __________________________________________________ satellite
(a) This artificial satellite is in a geostationary orbit. Complete the following sentences about satellites.
Choose from height period 24 hours position equator
A geostationary stationary satellite orbits the Earth once in________________
It stays in a fixed above the Earth’s surface. The ___________________ above the Earth’s surface
determines the orbital ____________ of the satellite. [3]
(b) Artificial satellites are used for transmitting information. They use electromagnetic waves to carry
the information. Describe how the satellites are used to transmit information.
____________________________________________________________________
_____________________________________________________________________
____________________________________________________________________[2]
(c) Artificial satellites have different uses. Geostationary satellites are used for communica-
tion. They have a high orbit. Other satellites have a low polar orbit. State one use for low
polar orbit satellites. _______________________________________________[1]
(d)Part of the Earth’s upper atmosphere is called the ionosphere. It is used for transmitting
information. Explain how radio waves are transmitted around the Earth using the
ionosphere. In your answer use your ideas about:
•what the ionosphere is
•what frequency of radio waves are used
•what happens to the waves when they strike the ionosphere.
______________________________________________________________________________________
_______________________________________________________________________________________
___________________________________________________________________________________[2]
2) This question is about the motion of two 15m/s
cars A and B
10m/s
A B
(a) (i) The speed of each car is shown. Speed is a scalar quantity. What other piece of
information would be needed to describe the car’s velocity?
[1]
(ii) Velocity is not a scalar quantity. What type of quantity is velocity? _________________[1]
(b)(i) Car B accelerates at 2 m/s2 for 3 seconds. Calculate the final speed of car B.
________________________________________________________________________
____________________________________________________________________[2]
(ii) Car B has a mass of 1 500 kg. Calculate the final momentum of car B.
________________________________________________________________
____________________________________________________________[2
(c) Car A catches up with car B. The driver does not brake quickly enough. The cars
collide. Write down two things about the force on the cars at the moment of impact.
At the moment of impact the forces exerted by the cars on each other are
and [2]

6. 3 (a) A ball is projected horizontally in the Earth’s gravitational field. Ignoring air resistance what happens to
the horizontal speed of the ball?
Put a ring around the correct answer. ball
the speed increases the speed stays the same the speed reduces [1]
(b) The ball moves towards the ground. What happens to the vertical speed of the ball?
[1]
(c) The ball has a resultant velocity. Explain what produces the resultant velocity of the ball.
Use your ideas about vectors in your answer.
_______________________________________________________________________________
____________________________________________________________________________[2]
4 This question is about white light entering a glass white light
prism. The light refracts and disperses into different red
colours
violet
(a) The amount of bending is different for each of the spectral colours. Complete the following
to explain why the amount of bending increases.
The amount of bending increases with a greater change of . [1]
(b) Red light is deviated less than blue light. Explain why. Use your ideas about refractive index in your
answer. _________________________________________________________________________
_____________________________________________________________________________________
________________________________________________________________________________[2]
5 This question is about the interference of waves. A
The diagram shows two sources of light A and B from area where rays overlap
two slits in a card in front of a lamp
B
(a) Interference is evidence for the wave nature of light. Name one other piece of evidence.
[1]
(b) The area where the waves overlap is where an interference pattern is produced. Describe the area of
interference pattern and explain how the waves produce it.
___________________________________________________________________________________
_________________________________________________________________________________[2]
6 This question is about convex lens principal focus
light through a convex lens axis
ray x
Ray X is travelling parallel to the axis of the lens. For the first part of this question (a), draw your answers on
the diagram above.
(a) (i) Complete the path of ray X after it passes through the lens. [1]
(ii) Draw the path of one other ray to show where the image of the object is formed. [1]
(b) The size of the object is 2 cm. The size of the image produced is 6 cm. Calculate the magnification.
[2]