Physics #7 Flashcards
transverse waves
those in which the direction of particle oscillation is perpendicular to propagation of the wave
Ex: wave in a stadium: moves around stadium but people just go up and down.
Ex: string whipped up and down attached at one point.
longitudinal waves
the particles of the wave oscillate parallel to the direction of propagation
Ex: person pushing in and pulling out a piston
Ex: slinky on a table and tapping it, kind of bumping into each other as the wave moves down.
propagation
movement and direction of energy transfer
maximum value of a wave is a ____
crest
wavelength
distance from one crest to the next (m)
frequency
number of wavelengths passing a fixed point per second (Hz) Cycles/second
period
seconds/cycle
equilibrium position
the central point around which waves oscillate
displacement and amplitude
displacement (x): describes how far a particular point on the wave is from the equilibrium position (expressed as a vector quantity)
amplitude (A): the maximum magnitude of displacement in a wave
what is the distance between a crest and trough called?
2x the amplitude
trough vs. crest
trough: bottom of the wave
crest: top of the wave
phase difference
for waves passing each other, calculating how in step or out of step they are
what is the phase difference for 2 waves that completely line up?
0 (360 degrees)
what is the phase difference for 2 waves that are completely out of phase?
180 or lambda/2
the principal of superposition
when waves interact with each other, the displacement of the resultant wave at any point is the sum of the displacements of the two interacting waves
constructive interference
when waves are perfectly in phase, the displacements always add together and the amplitude of the resultant is equal to the sum of the amplitudes of the two waves
destructive interference
when waves are perfectly out of phase, the displacements always counteract each other and the amplitude of the resultant wave is the difference between the amplitudes of the interacting waves
traveling wave
wave that moves
standing wave
the only apparent movement of the string is fluctuation of amplitude at fixed points along the length of the string. In reality the string is moving up and down (slow-mo) but looks like it is just standing there on top and bottom in real time.
nodes vs. antinodes
nodes: points in the wave that remain at rest (amplitude is 0)
antinodes: points midway between the nodes fluctuate with maximum amplitude
timbre
quality of sound
what frequencies are audible to healthy adults
20 Hz to 20,000 Hz
what produces the richest sounds
when objects vibrate at multiple natural frequencies (a fundamental pitch and multiple overtones) that are related to each other by whole number ratios.
the amplitude of wave increases if the ______ is nearly identical to the natural frequency
forced frequency
if the frequency of the periodic force is equal to a natural/resonant frequency of the system, then the system is said to be ______, and the amplitude of oscillation is at a maximum
resonating
damping/attenuation
a decrease in amplitude of a wave caused by an applied or nonconservative force.
what are the units for angular frequency
radians per second
wave speed
rate at which a wave transmits the energy or matter it is carrying
standing wave vs. traveling wave
traveling wave has nodes and antinodes that move with propagation
standing wave: nodes and antinodes do not move
are sound waves longitudinal or transverse waves?
longitudinal
applying a force at the natural frequency of a system will cause the system to _____
resonate
increases the amplitude of oscillations
can sound travel through the following: solids, liquids, gases, vaccum?
everything but vacuum because it needs deformable medium.
bulk modulus
a measure of a medium’s resistance to compression
how does the bulk modulus relate to solids, liquids, and gases
increases from gases to solids
what is the speed of sound in air at 20 degrees Celsiucs?
343 m/s
what medium and density is the speed of sound the fastest in?
solid with very low density
pitch
our perception of the frequency of sound
infrasonic vs. ultrasonic waves
infrasonic: less than 20 Hz
ultrasonic: more than 20,000 Hz
doppler effect
describes the difference between the actual frequency of a sound and its perceived frequency when the source of the sound and the sound’s detector are moving relative to one another.
echolocation and doppler
the sound bounces off of a surface and is reflected back to the animal. How long it takes to return and the change in frequency of the sound can be used to determine the position of objects in the environment and the speed at which they are moving.
in the doppler effect equation, if the detector or the source is not moving, then _______
the numerator or denominator is just the speed of the sound in the medium.
shock wave
speed of object is greater than speed of sound. Pressure difference created that can be detrimental to the other objects that it passes through
what are other words for loudness or volume of sound?
intensity
intensity
average rate of energy transfer per area across a surface that is perpendicular to the wave
power/area (w/m^2)
what is the surface area of a sphere
4(pi)r^2
useful for knowing distance traveled and area covered for a sound wave
what is the minimum intensity of hearing and the threshold of pain?
min: 1x10^-12 W/m^2
pain: 10 W/m^2
attenuation affects _____, ____ and ____, but not ______
amplitude, intensity, sound level
not frequency
how can sound volume vary due to interference effects?
beat frequency when two pitches are produced next to each other.
the points in a standing wave with no fluctuation in displacement are called ____
nodes
the points in standing waves with maximum fluctuation are called _____
antinodes
closed vs. open boundaries
closed: nodes
open: maximal oscillation
fundamental frequency of strings attached at both ends or open pipes
the first harmonic
the lowest frequency (longest wavelength) of a standing wave that can be supported by a given length of string
first overtone of strings attached at both ends or open pipes
n=2
n= 3 is known as the _____ for strings attached at both ends or open pipes
second overtone or third harmonic
for strings attached at both ends, the number of antinodes present will tell you the _____
harmonic
or number of half wavelengths = harmonic
for open pipes, the number of nodes will tell you ______
the harmonic
the harmonic in a closed pipe is equal to the number of ______
quarter wavelengths supported by the pipe
closed pipe
open at one end and closed on the other
ultrasound
uses high frequency sound waves outside the range of human hearing to compare the relative densities of tissue in the body
uses speed pf the wave and travel time to generate a graphical representation of borders and edges within the body by calculating the traversed distance.
doppler ultrasound
used to determine the flow of blood within the body by detecting the frequency shift that is associated with movement toward or away from the receiver
how is sound produced?
mechanical vibrations
to which properties of sound do amplitude and frequency correspond?
intensity (sound level) and pitch
if object and source are moving in same direction at same speed what is the perceived frequency compared to the actual frequency?
equal
____ is the increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object
resonance
shock waves are largest when ____
the objet is traveling at exactly the speed of sound
