Physics Ch 7. Waves and Sound Flashcards
Transverse waves
Have oscillations of wave particles perpendicular to the direction of wave propagation, includes electromagnetic waves
Propagation
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Longitudinal waves
Have oscillations of wave particles parallel to the direction of wave propagation, includes sound waves
Displacement in a wave
x - In a wave refers to how far appointed as from the equilibrium position expressed as a vector quantity
Amplitude in a wave
The magnitude of its maximum displacement
Crest
Maximum point of a wave or most positive displacement
Trough
Minimum point of a wave or point of most negative displacement
Wavelength
Lambda – the distance between two crests or two troughs
Frequency
F – the number of cycles per second, expressed in hertz
Angular frequency
Omega – another way of expressing frequency but expressed in radians per second
Period
T – the number of seconds it takes to complete a cycle, the inverse of frequency
Interference
Describe the ways in which waves interact to in space to form a resultant wave
Constructive interference
Occurs when waves are in exactly in phase with each other, the amplitude of the resultant wave is equal to the sum of the amplitude of the two interfering waves
Destructive interference
Occurs when waves are exactly out of phase with each other, the amplitude of the resultant wave is equal to the difference in amplitude between the two interfering waves
Partially constructive or partially destructive interference
Occur when two waves are not quite perfectly inner out of phase with each other, the displacement of the resultant wave is equal to the sum of the displacement of the two interfering waves
Traveling waves
Have continuously shifting points of maximum and minimum displacement
Standing waves
Produced by the constructive and destructive interference of two waves of the same frequency traveling in opposite directions in the same space
Anti-nodes
Points of maximum oscillation
Nodes
Points where there is no oscillation
Resonance
The increase in amplitude that occurs when a periodic force is applied at the natural or resonant frequency of an object
Natural/resonant frequency
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Damping
A decrease in amplitude caused by an applied or non-constructive force
Sound
Produced by mechanical disturbance of a material that creates an isolation of the molecules in the material
Sound propagation
Sounds propagates faster through solids, followed by liquids, and slowest through gases, within a medium, its density increases, the speed of sound decreases
Pitch
Related to the frequency of a sound
Doppler effect
A shift in the perceived frequency of a sound compared to the actual frequency of the omitted sound when the source of the sound and it’s detector are moving relative to one another
Source and detector moving toward each other
Apparent frequency will be higher than the emitted frequency
Source and detector are moving away from each other
Parent frequency will be lower than the emitted frequency
Source and detector moving in the same direction
The apparent frequency can be higher, lower, or equal to the emitted frequency when the two objects are moving in the same direction
Shock waves/sonic boom
When the source is moving at or above the speed of sound
Sound level
Related to sound intensity, intensity is related to a waves amplitude, intensity decreases over distance and some energy is lost to attenuation from frictional forces
Strings and open pipes
Open at both ends, support standing waves and the length of the stringer pipe is equal to some multiple of half wave lengths
Closed pipes
Closed at one end, also support standing waves in the length of the pipe is equal to some odd multiple of quarter wavelengths
Ultrasound
Sounds used medically for both imaging and treatment
Wave speed equation
v = f*lambda
Period equation
T = 1/f
Angular frequency equation
omega = 2pif=2*pi/T
Speed of sound equation
v = sqrt(B/rho)
Doppler effect equation
fprime=f*(v+/-v_d)/(v-/+v_s)
Intensity equation
I = P/A
Sound level equation
Beta = 10log(I/I_o)
Change in sound level equation
Beta_f = Beta_i +10log(I_f/I_i)
Beat frequency equation
f_beat = abs(f_1-f_2)
Wavelength of a standing wave in strings and open pipes
lambda = 2L/n
Frequency of a standing wave in strings and open pipes
f = nv/2/L
Wavelength of a standing wave in a closed pipe
lambda = 4*L/n
Frequency of a standing wave in a closed pipe
f = n*v/4/L
