Ch. 7: Waves and Sound Flashcards
Transverse waves
Have oscillations of wave particles perpendicular to the direction of wave propagation
Longitudinal waves
Have oscillations of wave particles parallel to the direction of wave propagation (e.g. sound waves)
Displacement
x, in a wave refers to how far a point is from the equilibrium position, expressed as a vector quantity
Amplitude
A, of a wave is the magnitude of its maximal displacement
Crest
Maximum point of a wave (point of most positive displacement)
Trough
Minimum point of a wave (point of most negative displacement)
Wavelength
λ, distance between two crests or two troughs
Frequency
f, number of cycles it makes per second, expressed in hertz (Hz)
Angular Frequency
ω, another way of expressing frequency, expressed in radians/sec
Period
T, number of seconds it takes to complete a cycle. Inverse of frequency
Interference
Describes the ways in which waves interact in space to from a resultant wave
Constructive interference
Occurs when waves are exactly in phase w each other. The amplitude of the resultant wave is equal to the sum of the amplitudes of the two interfering waves
Destructive interference
Occurs when waves are exactly out of phase w each other. Amplitude of the resultant wave is equal to the diff in amplitude between two interfering waves
Partially constructive and partially destructive interference
Occur when two waves are not quite perfectly in or out of phase w each other. Displacement of the resultant wave is equal to the sum of displacements of the two interfering waves
Traveling waves
Have continuously shifting points of max and min 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
Antinodes
Points of max oscillation
Nodes
Points where there is no oscillation
Resonance
Increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object
Damping
Decrease in amplitude caused by an applied or nonconservative force
Sound
Produced by mechanical disturbance of a material that creates an oscillation of the molecules in the material
Sound propagation
Sound propagates through all forms of matter (but not a vacuum). Propagates fastest through solids, followed by liquids, and slowest through gases– within a medium, as density increases, the speed of sound decreases.
Pitch
Of a sound, related to its frequency
Doppler Effect
Shift in the perceived frequency of a sound compared to the actual frequency of the emitted sound when the source of the sound and its detector ae moving relative to one another
- the apparent frequency will be higher than the emitted frequency when he source and detector are moving toward each other
- the apparent frequency will be lower than the emitted frequency when the source and detector are moving away from each other
- the apparent frequency can be higher, lower, or equal to the emitted frequency when the 2 objects are moving in the same direction, depending on their relative speeds
Shock waves (sonic booms)
Can form when the source is moving at or above the speed of sound
Sound level
Related to its intensity, loudness or volume
Intensity
Related to a wave’s amplitude, decreases over distance and some energy is lost to attenuation (damping) from frictional forces
Open pipes
Strings and open pipes (open at both ends) support standing waves, and the length of the string or pipe is equal to some multiple of half-wavelengths
Closed pipes
Closed at one end, also support standing waves, and the length of the pipe is equal to some odd multiple of quarter-wavelengths
Ultrasound
Sound is used medically in ultrasound machines for both imaging (diagnostic) and treatment (therapeutic) purposes
