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Essential Question?• How does a wave transfer energy?
Waves• Wave – a disturbance that carries energy through matter or space• For an example;• Ocean waves disturb water and transfer energy through• During an earthquakes, energy transferred in powerful waves that travel through the earth• Light is a type of wave that can travel through an empty space from one place to another.
Wave – a disturbance thatcarries energy through matteror spaceMechanical waves –require amedium to travel through
Medium – something thatsomething travels throughSound travels through air,therefore, air is the medium.Waves in a pond travelthrough water, therefore,water is the medium.
Waves1. You have learned how Newtons laws of motion and principles of conservation of energy govern the behavior of particles.2. These laws and principles also govern the motion of waves.3. There are many types of waves that transmit energy even the ones you cannot see.
• Mechanical Waves - A mechanical wave is a disturbance that travels through some material or substance called the medium for the wave.• Note: The medium as a whole does not travel with the wave.• Note: A wave transfers energy, but it does not transfer any material or substance outward from the source.
Waves carry energy becausethey can do work.Water waves can move an objectup and down or throw it on abeach.Sound waves move your eardrumand you hear.Light waves allow your eye to seeand can make an image on film.
Most waves are caused by avibration.Particles in a medium can vibrateeither up and down or back andforth.Waves are classified by thedirection that the particles in themedium move as a wave passesby.
Wave Phenomenon• Wave phenomenon, energy can move from one location to another, yet the particles of matter in the medium return to their fixed position. A wave transports its energy without transporting matter.
Two types of Waves• Transverse waves• Longitudinal wave
2. Longitudinal wave – particlesvibrate parallel to the directionof the wave motion
Sound Waves• A sound wave traveling through air is a classic example of a longitudinal wave.
1. Transverse waves – particlesmove perpendicular to the motionof the wave
Transverse waves• Waves in the electromagnetic spectrum are Transverse Waves
Parts of a Transverse Wave Wavelength Crest CrestNormal AmplitudeTrough Trough Wavelength
Parts of a Wave• Crest - each high point of a wave• Trough – each low point• Wave length – distance between points where the wave pattern repeats itself• Amplitude – any periodic motion, the maximum distance an object moves from equilibrium
Parts of a Longitudinal Wave Rarefactions Compressions
Rarefactions• Rarefactions - are regions of low air pressure Rarefactions Compressions
Compressions• Compressions are regions of high air pressure Rarefactions Compressions
The difference between Transverse and Longitudinal waves• Transverse waves -are those in which displacement of particle is perpendicular to that of propagation of wave.• Longitudinal waves - are those in which displacement of the particle is in a direction parallel to that of propagation.
Period – In a periodic motion, the amount oftime required for an object to repeat onecomplete cyclePeriodic motion- wave move up and downat the same rate PERIOD Example: 1 wave every 20 seconds
Frequency – The number of wave crest thatpass a point during one second.( expressed in hertz) Example: 3 waves per Second (3Hz)
Frequency Equation• The frequency of a wave length is equal to the reciprocal of the period• F=1/T
Hertz• The symbol for frequency is f.• The SI unit is hertz (Hz).• One vibration/wave per second is 1 Hz.• Two vibrations/wave per second is 2 Hz.
Wave length Equation• The wavelength of a wave is equal to the velocity divided by the frequency• Wavelength = V/f
Period & FrequencyDepends on?The sourceDoes Not depend on?The medium and wave’s speed
What affects the waves speed?The speed of a wave depends on the medium in which the wave is traveling.
Light waves can movethrough air faster than they canmove through water. This is why apencil will look broken when it isplaced in a glass of water.Exactly where does the pencillook broken?At the junction of the two differentmediums.
Sound travels faster in water than in air. Sound travels faster in solids than in liquids. Why do you think this is so?The closer the molecules are, theeasier it will be for the moleculesto bump into one another. Thisallows the vibrations to movefaster, thus allowing the wave tomove faster.
Comparing Light & Sound Waves• Light waves can move through air faster than they can move through water. Because?....• Once the Light Wave enters another medium it changes directions and slows down.• Sound travels faster in water than in air. Because?....• The closer the molecules are, the easier it will be for the molecules to bump into one another. This allows the vibrations to move faster, thus allowing the wave to move faster.
Doppler EffectDoppler effect – a change in the frequency of a wave when the source or observer is moving
Reflection• bouncing back of a wave when it meets a surface
Refraction• the bending of waves as they pass from one medium into another
Diffraction• bending of waves as they pass through narrow openings or around sharp corners
Interference• Interference – the combination of two or more waves that exist in the same place at the same time
Interference Waves• Interference of light is difficult to observe since the waves are so small and the vibrations so rapid.• However, interference takes place with any kind of wave motion, and the effects of interference can be more easily seen by the examining the behavior of water waves, which are in many ways similar to light waves, but travel more slowly and are more easily noticeable.
Constructive interferenceConstructive interference – waves combine to make a larger wave
Destructive interference• Destructive interference – waves combine to make a smaller wave
Interference – the combination oftwo or more waves that exist in thesame place at the same timeConstructive interference – wavescombine to make a larger waveDestructive interference – wavescombine to make a smaller wave
Review• Mechanical waves (sound, ocean waves, seismic) require a medium (air, water, ground) to travel through.
Electromagnetic WavesElectromagnetic waves – waves that are caused by a disturbance in electric and magnetic fields and does not require a medium to travel throughElectromagnetic waves are produced by the vibration of charged particles
Electromagnetic Waves• Electromagnetic waves are created by the vibration of an electric charge.• This vibration creates a wave which has both an electric and a magnetic component.• An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c).
Examples of electromagnetic waves: Lower energy Radio waves Longer wavelength Microwaves Infrared waves Visible light waves Ultra-violet waves Higher energy X-rays Shorter wavelength