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36 Cards in this Set
- Front
- Back
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wave
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transfer of momentum and energy from one point to another
3 types: 1. mechanical 2. electromagnetic 3. matter |
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Mechanical waves
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obey law of classical physics
require some medium through which to propogate non dispersive medium is momemtarily displaced by wave and then returned to its position 2 types: 1. transverse wave 2. longitudinal wave |
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transverse wave
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medium is displaced perpendicularly to direction of wave propagation
ex: wave on a string can be represented by sine function (vertical displacement of medium with respect to time or displacement of wave) |
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longitudinal wave
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medium displaced parallel to direction of wave propagation
ex: sound wave in air can be represented by sine function (change in pressure or horizontal displacement of medium with respect to time or displacement of wave) |
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wavelength
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if x-axis is displacement of wave, it is measured from any point in wave to point where wave begins to repeat itself
ex: trough to trough or peak to peak units of meters |
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wave
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transfer of momentum and energy from one point to another
3 types: 1. mechanical 2. electromagnetic 3. matter |
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Mechanical waves
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obey law of classical physics
require some medium through which to propogate non dispersive medium is momemtarily displaced by wave and then returned to its position 2 types: 1. transverse wave 2. longitudinal wave |
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transverse wave
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medium is displaced perpendicularly to direction of wave propagation
ex: wave on a string can be represented by sine function (vertical displacement of medium with respect to time or displacement of wave) |
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longitudinal wave
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medium displaced parallel to direction of wave propagation
ex: sound wave in air can be represented by sine function (change in pressure or horizontal displacement of medium with respect to time or displacement of wave) |
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wavelength
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if x-axis is displacement of wave, it is measured from any point in wave to point where wave begins to repeat itself
ex: trough to trough or peak to peak units of meters |
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frequency (f)
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number of wavelengths that pass a fixed point in 1 second
measured in hertz (Hz) or cycles/sec (1/s) |
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velocity
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product of wavelength and frequency
v = wf dictated by medium through which wave travels change in frequency or wavelength does not change velocity of wave |
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period (T)
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reciprocal of frequency
number of seconds required for 1 wavelength to pass a fixed point where x-axis is time, any point on wave to next point where wave begins to repeat itself T = 1/f |
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amplitude (A)
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maximum displacement from zero
always positive |
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medium
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only thing that affects velocity
1. medium's resistance to change in shape (elasticity) 2. medium's resistance to change in motion (inertia) for a gas, velocity always increases with temperature elastic component stores PE inertial component stores KE |
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intensity (I)
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power of waves
rate at which waves transfer energy units of W/m^2 proportional to A^2 and f^2 |
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decibels (dB)
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dB = 10log (I/Io)
dB: decibels I: intensity Io: threshold intensity of human hearing I > 10X, dB > 10 I > 10^2, dB > 20 I > 10^3, dB > 30 I > 10^4, dB > 40 ex: I > from 30 to 3000, dB > 20 (added 2 zeros to I, so add 20 to dB) |
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phase
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relates to its wavelength, frequency, place and time of origin
horizontal shift of a wave on a graph in phase: same wavelength & begin at same point out of phase: same wavelength & different distances but arrive at same point |
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constructive interference
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waves occupy same space and superposition occurs
sum of displacements results in greater displacement |
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destructive interference
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occurs when sum of displacements results in smaller displacement
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beats
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2 waves with slightly different frequencies are superimposed
at some points waves will experience constructive interference and at others destructive interference points will alternate with frequency equal to difference between frequencies of original 2 waves alternating increase and decrease in noise intensity pitch correlates to frequency: high note = high pitch = high frequency fbeat = |f1 - f2| |
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wave reflection
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if wave reflects off denser medium, wave is inverted
if wave reflects off less dense medium, wave is upright when wave reflects from 1 medium to the next, wavelength changes but frequency remains the same |
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Node
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2 waves traveling in opposite directions with same wavelength, point of intersection has zero displacement
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antinode
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2 waves traveling in opposite directions with same wavelength, point of maximum constructive interference, greatest amplitude
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standing wave
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string holds still at nodes and moves violently up and down at antinodes
endless sine waves, with same wavelength, traveling in opposite directions |
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harmonic series
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list of wavelengths from largest to smallest of possible standing waves
harmonics are number from longest to shortest wavelength |
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1st harmonic (fundamental wavelength)
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longest wavelength
created with fewest number of nodes = 2 distance from 1 wall to other is 1/2 wavelength each successive harmonic is created by adding a wavelength |
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pipe open or closed at both ends or string tide at both ends
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L = (nfn)/2 (n= 1, 2, 3, etc)
L: distance between 2 ends of string n: number of harmonic both ends are nodes |
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pipe open or closed at 1 end or string tide at 1 end
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L = (nfn)/4 (n= 1, 3, 5, etc)
L: distance between 2 ends of string n: number of harmonic one end is an antinode |
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resonate
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standing waves cause string to resonate
vibrate at its natural frequency or resonant frequency v = fw v: velocity f: resonant frequency w: wavelength velocity is constant for a given medium at resonant frequency, structure experiences maximum vibration velocities and displacement amplitudes |
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resonance
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situation where natural frequency and driving frequency are equal
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simple harmonic motion
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it is a sinusoidal function in time
acceleration is proportional to displacement but opposite in sign acceleration and displacement are related by f^2 oscillation between KE and PE, no energy is lost to surroundings ex: a mass bouncing on the end of a massless spring pendulum swinging at a small angle plant's orbit WACK'EM: w = square root (k/m) angular frequency for mass on a string WIGGLE: w = square root (g/L) angular frequency for pendulum |
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doppler effect
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results because waves are unaffected by speed of source with produces them
(change f/fs) = v/c f: frequency fs: source frequency v: relative velocity c: wave velocity (change w/ws) = v/c w: wavelength ws: source wavelength v: relative velocity c: wave velocity if wavelength shorten: blue if wavelengths lengthen: red |
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Wave equations
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v = fw
T = 1/f |
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Sound equations
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dB = 10log(I/Io)
fbeat = |f1 - f2| L = (nwn)/4 (n= 1, 3, 5, etc) L = (nwn)/2 (n= 1, 2, 3, etc) |
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Doppler effect equations
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(fo - fs)/fs = v/c
(wo - ws)/ws = v/c |
