Waves and Sound Flashcards
transverse waves
those in which the direction of particle oscillation is perpendicular to the propagation
longitudinal waves
ones in which the particles of the wave oscillation parallel to the direction of propagation; the wave particles are oscillating in the direction of energy transfer
propagation speed of wave
v = f•λ
period
T = 1/f
angular frequency
ω = 2πf = 2π/T
radians/sec
in phase vs out of phase
crests coincide
vs
crest and trough at same time for example, λ/2
constructive interfere
- waves are perfectly in phase
- displacements always add together and the amplitude of the resultant is equal to the sum of the amplitudes of the two waves
destructive interference
- waves are perfectly out of phase
- displacements always counteract each other and the amplitude of the resultant wave is the difference between amplitudes of the interacting waves
nodes
- points in the wave that remain at rest
- amplitude is constantly zero
antinode
points midway between the nodes fluctuate with maximum amplitude
damping
a dec in amplitude caused by an applied or nonconservative force
the speed of sound
v = sqrt (B/ρ)
B: bulk modulus, a measure of the medium’s resistance to compression
speed of sound in air at about 20°C is 343 m/s
Doppler Effect equation
fD’ = fS [(v +/- vD)/(v -/+ vS)]
away is negative for the observer
towards is negative for the source
intensity
I = P/A
W/(m^2)
sound level
β = 10•log(I/I0)
β is in units of dB
change in sound frequency
βf = βi + 10•log(If/Ii)
beat frequency
fbeat = |f1 - f2|
f1 and f2 represent two frequencies that are close in pitch
closed boundaries
- those that do not allow oscillation and that correspond to nodes
- closed end of a pipe and the secured end of a string
open boundaries
- allow maximum oscillation
wavelength of a standing wave (strong or open pipe)
λ = 2L/n
n is harmonic which corresponds to the number of half-wavelengths supported by the string
frequency of string and open pipe
f = nv/2L
wavelength of a standing wave in a closed pipe
λ = 4L/n
n is only odd integers and in this case represents the number given by the number of quarter-wavelengths supported by the pipe
frequency of a standing wave in a closed pipe
f = nv/4L
ultrasound
- high frequency sound waves outside the range of human hearing to compare the relative densities of tissue in the body
- can be used to break up a kidney stone
- ## inc blood flow to certain areas of injury
