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**Physics Waves Lecture Notes Download**

PDF Document Waves.pdf Powerpoint Slides Waves.ppt

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**Types of Waves Compression wave Transverse Wave**

oscillations are in the direction of motion Transverse Wave oscillations are transverse to the direction of motion

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**Physical Examples Compression wave Transverse Wave sound waves**

earthquake P-waves Transverse Wave water waves earthquake S-waves light waves

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**Wave Parameters Wavelength (l) length or size of one oscillation**

Amplitude (A) strength of disturbance (intensity) Frequency (f) repetition

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**Wave Properties Waves are oscillations and they transport energy.**

The energy of a wave is proportional 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: amplitude corresponds to loudness LIGHT: amplitude corresponds to brightness

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What is the Wave length? Measure from any identical two successive points 5 10 15 20 25 30 35 40

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What is the Wave length? Measure from any identical two successive points 5 10 15 20 25 30 35 40 = 20

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What is the Wave length? Measure from any identical two successive points There are 4 complete oscillations depicted here ONE WAVE = 1 COMPLETE OSCILLATION 5 10 15 20 25 30 35 40 = 20

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Frequency Frequency = number of WAVES passing a stationary point per second (Hertz)

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Frequency and Period Frequency (f) = number of oscillations passing by per second Period (T) = length of time for one oscillation T = 1/f f = 1/T If a source is oscillating with a period of 0.1 seconds, what is the frequency? f = 1/(0.1) = 10 Hz It will complete 10 oscillations in one second. (10 Hz) If a source oscillates every 5 seconds, its period is 5 seconds, and then the frequency is f = 1/5 = 0.2 Hz.

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**Wave Speed Wave speed depends on the wavelength and frequency.**

wave speed v = l f Which animal can hear a shorter wavelength? Cats (70,000 Hertz) or Bats (120,000 Hertz) l = v/f

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**Wave Speed v = l f Which animal can hear a shorter wavelength?**

Cats (70,000 Hertz) or Bats (120,000 Hertz) l = v/f Higher frequency = shorter wavelength Lower frequency = longer wavelength

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Sonic Boom v > vsound

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Doppler Effect Change in frequency of a wave due to relative motion between source and observer. A sound wave frequency change is noticed as a change in pitch.

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**Radial Velocity Convention**

True Velocity Radial = Line of Sight Component Observer Radial Velocity > 0 Moving Away No Doppler Shift Transverse motion Radial Velocity < 0 Moving Toward

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Doppler Effect Light

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**Line of Sight Only sensitive to motion between source and observer**

ALONG the line of sight.

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**Doppler Effect for Light Waves**

Change in frequency of a wave due to relative motion between source and observer. c = l f speed of light = wavelength x frequency c = 3 x 108 m/s E = hf = hc/l energy of a light wave, a photon of frequency (f) or wavelength (l) h = planck’s constant 6.63 x J-sec A light wave change in frequency is noticed as a change in “color”.

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**Wavelength Doppler Shift**

l0 = at rest (laboratory) wavelength l = measured (observed) wavelength Dl = l - l0 = difference between measured and laboratory wavelength vr/c = Dl/l0 vr = (Dl/l0)c radial velocity

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Two Equal Waves Upon arriving in the same place, they add constructively

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**Constructive Interference**

Waves combine without any phase difference When they oscillate together (“in phase”)

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Wave Addition Amplitude ~ Intensity

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Two Opposite Waves Upon arriving in the same place, they cancel, destructively

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**Destructive Interference**

Waves combine differing by multiples of 1/2 wavelength They oscillate “out-of-phase”

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Wave Subtraction

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**Interference Water waves from two oscillating sources**

Computer Simulation Ripple Tank

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Two Slit Interference

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**Two Slit Constructive Interference**

Path Length Difference = multiples of the wavelength l

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Two Slit Interference Slits are closer together, path length differences change

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**Light or Dark? Path Length Differences = l, Waves arrive in phase**

Path Length Differences = 1/2 l, Waves arrive out of phase

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**Wave Properties Amplitude:**

Size of wave (perpendicular to direction of propagation) Proportional to Intensity(Sound loudness, Light brightness) Wavelength: l Size of wave (in the direction of propagation) Frequency: Number of waves passing a fixed position per second f (cycles/second, Hertz) Wave Speed: v = l f Frequency increases Frequency decreases Energy increases Energy decreases Wavelength decreases Wavelength increases

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