2 There are two ways to transmit information and energy in our universe: Particle MotionandWave Motion
3 Light and SoundBoth are vibrations ofdifferent kinds.Vibration -Wiggle in timeWave -Wiggle in space
4 1. VIBRATION OF A PENDULUM Demo - MetronomeDemo - Bowling ball pendulumVideo – Three Bowling BallsVideo – Swinging ExamplesDemo - Pendulum with extra massTime to swing depends on the length but not the mass of the pendulum.
5 Period of a Pendulum T is the period, the time for one vibration. l is the length of the pendulum.g is the acceleration due to gravity.Galileo discovered this.Period (T ) is independent of the mass of the bob.
6 Pendulum Uses: Timing Oil prospecting Walking When the oscillation is small, the motion is called simple harmonic motion and can be described by a simple sine curve.
7 2. WAVE DESCRIPTIONFrequency ( f ) is the number of vibrations per unit of time made by the vibrating source.Units -cycles per second1/sHertz (Hz)
8 Picture of a Transverse Wave CrestlWavelengthAA - AmplitudeTroughBaseline
9 Wavelength (l)Distance between adjacent crests in a transverse waveDistance a wave travels during one vibrationUnits- meters or feet
10 The period (T ) of a vibration is the time required to make one vibration. The period (T ) of a wave is the time required to generate one wave.It is also the time required for the wave to travel one wavelength.
13 3. WAVE MOTION Energy is transported by particles or waves. A wave is a disturbance transmitted through a medium.Exception: light does not require a medium.
14 Demo – Waves on a ropeA disturbance moves through the medium.Elements of the medium vibrate.Examples:ripples on waterwheat waves
15 4. WAVE SPEEDThe average speed of anything is defined as
16 or Remember that Therefore For a wave, if the distance traveled is a wavelength (l), then the time to travel this distance is the period (T ). ThenorRemember thatTherefore
17 is true for all waves.Demo - Complete Bell Wave MachineNote: v is dictated by the medium.(must change medium to change v)f is dictated by the source.(must change the source to change f )
18 5. TRANSVERSE WAVES Video - Slinky Transverse Waves Examples: string musical instrumentsripples on waterelectromagnetic wavesDemo – Human Waves (Include Standing)
19 6. LONGITUDINAL WAVES Video - Slinky Longitudinal Waves Parameters Rarefactions are regions of low density.Compressions (condensations) are regions of high density.l is the distance between successive rarefactions or successive compressions.
20 Demo - SlinkyCompressionsRarefactionsExample: sound in air
21 7. INTERFERENCEVideo - Superposition of WavesSlide - Interference
29 Standing WavesWhen two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still.” It is a changing interference pattern.Demo - Rope and strobe
30 There is no vibration at a node. lThere is no vibration at a node.There is maximum vibration at an antinode.l is twice the distance between successive nodes or successive antinotes.
31 Video - Drumhead Vibrations Demo - Organ pipe and tuning forkDemo – Standing waves in sheet metalAnother example: musical instruments
32 8. DOPPLER EFFECTRefers to the change in frequency when there is relative motion between an observer of waves and the source of the waves
33 Video - Doppler Effect in Air Video - Doppler Effect in a Ripple TankURL– Doppler Movie (htm)Demo – Doppler Rocket
34 When a source of waves and an observer of waves are getting closer together, the observer of the waves observes a frequency for the waves that is higher than the emitted frequency.When a source of waves and an observer of waves are getting farther apart, the observer of the waves observe a frequency for the waves that is lower than the emitted frequency.
35 All waves exhibit the Doppler effect. A particularly interesting example is used by astronomers to determine if light emitting objects (such as stars) are getting closer to us or farther away.On average most stars are moving farther away, and their light spectra are “red shifted.”
36 Red Shift Lab Absorption Spectrum of Element X Red ShiftedStar Absorption Spectrum of Element XStar is moving away from us.
37 Police use the Doppler effect to catch speeding motorists. Radar bounced off a spinning planet can exhibit a Doppler effect and lead to a determination of the spin rate of the planet.This was used to discover that Venus has a retrograde spin.
43 The familiar bow wave generated by a speedboat knifing through the water is a non-periodic wave produced by the overlapping of many periodic circular waves. It has a constant shape.
44 10. SHOCK WAVESJust as circular waves move out from a swimming bug, spherical waves move out from a flying object. If the object flies faster than the waves, the result is a cone-shaped shock wave.Demo - Cone of WavesThere are two booms, one from the front of the flying object and one from the back.
45 Demo – Crack whipVideo – Sonic Booms OnlineVideo - FB-111 Sonic BoomVideo – F-14 Sonic BoomURL – More BoomWord Doc - Sonic BoomThe boom is not produced just when the flying object “breaks” through the sound barrier.
46 Subsonic- slower than the speed of sound- faster than the speed of soundSupersonicspeed of objectMach Number=speed of sound