Waves and Sound

Question 1

have oscillations of wave particles perpendicular to the direction of wave propagation (movement) (e.g. electromagnetic waves)

Answer 1

transverse waves

Question 2

have oscillations of wave particles parallel to the direction of wave propagation (e.g. sound waves)

Answer 2

longitudinal waves

Question 3

refers to how far a point is from the equilibrium position in a wave, expressed as a vector quantity

Answer 3

displacement (x)

Question 4

magnitude of maximal displacement of wave

Answer 4

amplitude (A)

Question 5

maximum point of wave, point of most positive displacement

Answer 5

crest

Question 6

minimum point of wave, point of most negative displacement

Answer 6

trough

Question 7

distance between two crests or troughs of wave

Answer 7

wavelength (λ)

Question 8

number of cycles a wave makes per second; expressed in Hertz (Hz)

Answer 8

frequency (ƒ)

Question 9

frequency (ƒ)

Answer 9

v = ƒλ

where:
v = propagation speed
λ = wavelength

Question 10

number of seconds a wave takes to complete a cycle; inverse of frequency

Answer 10

period (T)

Question 11

period (T)

Answer 11

T = 1/ƒ

where:
ƒ = frequency

Question 12

another way of expressing frequency; expressed in radians/second (rad/sec)

Answer 12

angular frequency (ω)

Question 13

angular frequency (ω)

Answer 13

ω = 2πƒ = 2π/T

where:
ƒ = frequency
T = period

Question 14

describes the ways in which waves interact in space to form a resultant wave

Answer 14

interference

Question 15

type of interference:

occurs when waves are exactly in phase with each other; amplitude of resultant wave equals sum of two interfering waves

Answer 15

constructive interference

Question 16

type of interference:
occurs when waves are exactly out of phase with each other; amplitude of resultant wave equals difference of two interfering waves

Answer 16

destructive interference

Question 17

type of interference:
occurs when two waves are not quite perfectly in or out of phase with each other; the displacement of the resultant wave equals the sum of the displacement of the two interfering waves

Answer 17

partially constructive or destructive interference

Question 18

have continually shifting points of maximum and minimum displacement

Answer 18

traveling waves

Question 19

are produced by the constructive and destructive interference of two waves of the same frequency traveling in opposite directions in the same space

Answer 19

standing waves

Question 20

points of maximum oscillation

Answer 20

antinodes

Question 21

points where there is no oscillation

Answer 21

nodes

Question 22

the increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object

Answer 22

resonance

Question 23

a decrease in amplitude caused by an applied or nonconservative force

Answer 23

damping (attenuation)

Question 24

is produced by mechanical disturbance of a material that creates an oscillation of the molecules in the material; propagates through all forms of matter (but not a vacuum); propagates fastest through solids, then liquids, and slowest through gases; as density of medium increases the speed of sound decreases

Answer 24

sound

Question 25

speed of sound through a medium (v)

Answer 25

v = √(B/ρ) where: B = Bulk modulus ρ = density

Question 26

a measure of the medium's resistance to compression; increases from gas to liquid to solid

Answer 26

Bulk modulus (B)

Question 27

our perception of the frequency of sound

Answer 27

pitch

Question 28

a 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 are moving relative to one another

Answer 28

Doppler effect

Question 29

Doppler effect

Answer 29

ƒ' = ƒ ((v ± v(D)) / (v ∓ v(S)) ``` where: ƒ' = perceived frequency ƒ = actual frequency v = speed of sound in medium v(D) = speed of detector v(S) = speed of source ``` signs: top sign- used when source and detector moving toward one another bottom sign- used when source and detector moving away from one another

Question 30

will be higher than emitted frequency when the source and detector are moving toward each other; will be lower than emitted frequency when the source and detector are moving away from each other

Answer 30

apparent frequency

Question 31

can occur when source is moving at or above the speed of sound

Answer 31

shock wave (sonic boom)

Question 32

the way in which we perceive the intensity of a sound

Answer 32

loudness or volume of sound

Question 33

average rate of energy transfer per area across a surface that is perpendicular to the wave; power transported per unit area; units = W/m^2 (W is watts); decreases over distance and some energy is lost to damping (attenuation) from frictional forces

Answer 33

intensity

Question 34

intensity (I)

Answer 34

I = P/A where: P = power A = area

Question 35

support standing waves, and the length is equal to some multiple of half-wavelengths

Answer 35

strings and open pipes

Question 36

a positive, nonzero integer that corresponds to the number of half-wavelengths supported

Answer 36

harmonic of string or open pipe (n)

Question 37

equation that relates wavelength of standing wave and length of string or open pipe:

Answer 37

λ = 2L/n where: λ = wavelength L = length n = harmonic (1,2,3,...)

Question 38

equation of possible frequencies of string or open pipe:

Answer 38

ƒ = nv/2L ``` where: ƒ = frequency n = harmonic (1,2,3,...) v = wave speed L = length ```

Question 39

number of antinodes will tell you which harmonic it is

Answer 39

string

Question 40

number of nodes will tell you which harmonic it is

Answer 40

open pipe

Question 41

the lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string or pipe; given by n=1

Answer 41

fundamental frequency (first harmonic)

Question 42

second harmonic = ____ third harmonic = ____ ...

Answer 42

first overtone | second overtone

Question 43

all the possible frequencies that a string or pipe can support

Answer 43

harmonic series

Question 44

support standing waves, length is equal to some odd multiple of quarter-wavelengths

Answer 44

closed pipe

Question 45

a positive, nonzero, odd integer that corresponds to the number of quarter-wavelengths supported

Answer 45

harmonic of closed pipe (n)

Question 46

equation that relates wavelength of standing wave and length of closed pipe:

Answer 46

λ = 4L/n where: λ = wavelength L = length n = harmonic (1,3,5,...)

Question 47

equation of possible frequencies of closed pipe:

Answer 47

ƒ = nv/4L ``` where: ƒ = frequency n = harmonic (1,3,5,...) v = wave speed L = length ```

Question 48

medical application of sound, used for both imaging (diagnostic) and treatment (therapeutic) purposes

Answer 48

ultrasound