Waves Power Point

8/2/2019 Waves Power Point

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PHYSICS 324:

WAVES


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Types of Waves

Longitudinal wave

oscillations are in the

direction of motion

(parallel to the motion)

Transverse Waveoscillations areperpendicular

to the direction of

Motion


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Physical Examples

Longitudinal wave

sound waves

earthquake P-waves

Transverse Wave

water waves

earthquake S-waves light waves


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Wave ParametersWavelength (P) length orsize of one oscillation

Amplitude (A) strength of disturbance (intensity)

Frequency (f) r epetition / how often they occurper

second


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Wave PropertiesWaves are oscillations and they transport energy.

Theenergy of a wave isproportional to its frequency.

Fast oscillation = high frequency = high energy

Slow oscillation = low frequency = low energy

The amplitude is a measure of the wave intensity.

SOUND: amplitudecorresponds to loudness

LIGHT: amplitudecorresponds to brightness


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What is the Wave length? Measure from any identical two successivepoints

5 10 15 20 25 30 35 40 (nm)


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What is the Wave length?

Measure from any identical two successivepoints

5 10 15 20 25 30 35 40

30nm 10nm = 20nm

(nm)


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What is the Wave length? Measure from any identical two successivepoints

There are 4 complete oscillations depicted here

ONE WAVE = 1 COMPLETE OSCILLATION

5 10 15 20 25 30 35 40

22.5nm - 2.5nm = 20nm

(nm)


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Frequency Frequency = number of WAVES passing a stationarypoint

persecond (Hertz)


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Frequency and PeriodFrequency (f) = number of oscillationspassing bypersecond

Period (T) = length of time for one oscillation

T = 1/f f= 1/T

If a source is oscillating with a period of 0.1seconds,

what is the frequency?


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f= 1/(0.1) = 10 HzIt will complete10 oscillations in onesecond. (10

Hz)

If a source oscillatesevery5seconds, itsperiod is

5seconds, and then the frequency is????


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f= 1/5 = 0.2 Hz.


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Wave Speed

Wavespeed depends on the wavelength and frequency.

wavespeed v = Pf

Which animal can hear a shorter wavelength?

Cats (70,000 Hertz) or Bats (120,000 Hertz)

P = v/f


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Wave Speedv = Pf

Which animal can hear a shorter wavelength?

Cats (70,000 Hertz) or Bats (120,000 Hertz)

P = v/f

Higher frequency = shorter wavelength

Lower frequency = longer wavelength


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Doppler Effect

Change in frequency of a wave due to relative motionbetween source and observer.

A sound wave frequencychange is noticed as a change in

pitch.


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Doppler Effect forLight Waves

Change in frequency of a wave due to relative motion betweensource and observer.

c = Pf speed of light = wavelength x frequency

c = 3 x 108

m/s

E = hf = hc/Penergy of a light wave, a photon

of frequency (f) or wavelength (P

h = plancksconstant 6.63 x 10-34

J-sec

A light wavechange in frequency is noticed as a change

in color.


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Constructive Interference Wavescombine without anyphase difference

When they oscillate together (in phase)


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Wave AdditionAmplitude ~ Intensity


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Destructive Interference Wavescombine differing by multiples of1/2 wavelength

They oscillate out-of-phase


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Wave Subtraction


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Amplitude:

Size of wave (perpendicular to direction ofpropagation)Proportional to Intensity(Sound loudness,Light brightness)

Wavelength:

PSize of wave (in the direction ofpropagation)

Frequency:

Number of wavespassing a fixed positionpersecond

f (cycles/second, Hertz)

Wave Speed: v = Pf

Frequency increases Frequency decreases

Energy increases Energy decreases

Wavelength decreases Wavelength increases

Wave Properties

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