Waves and Sound

Question 1

transverse waves

Answer 1

those in which the direction of particle oscillation is perpendicular to the propagation

Question 2

longitudinal waves

Answer 2

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

Question 3

propagation speed of wave

Answer 3

v = f•λ

Question 4

period

Answer 4

T = 1/f

Question 5

angular frequency

Answer 5

ω = 2πf = 2π/T

radians/sec

Question 6

in phase vs out of phase

Answer 6

crests coincide

vs

crest and trough at same time for example, λ/2

Question 7

constructive interfere

Answer 7

• 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

Question 8

destructive interference

Answer 8

• 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

Question 9

nodes

Answer 9

• points in the wave that remain at rest
• amplitude is constantly zero

Question 10

antinode

Answer 10

points midway between the nodes fluctuate with maximum amplitude

Question 11

damping

Answer 11

a dec in amplitude caused by an applied or nonconservative force

Question 12

the speed of sound

Answer 12

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

Question 13

Doppler Effect equation

Answer 13

fD’ = fS [(v +/- vD)/(v -/+ vS)]

away is negative for the observer

towards is negative for the source

Question 14

intensity

Answer 14

I = P/A

W/(m^2)

Question 15

sound level

Answer 15

β = 10•log(I/I0)

β is in units of dB

Question 16

change in sound frequency

Answer 16

βf = βi + 10•log(If/Ii)

Question 17

beat frequency

Answer 17

fbeat = |f1 - f2|

f1 and f2 represent two frequencies that are close in pitch

Question 18

closed boundaries

Answer 18

• those that do not allow oscillation and that correspond to nodes
• closed end of a pipe and the secured end of a string

Question 19

open boundaries

Answer 19

• allow maximum oscillation

Question 20

wavelength of a standing wave (strong or open pipe)

Answer 20

λ = 2L/n

n is harmonic which corresponds to the number of half-wavelengths supported by the string

Question 21

frequency of string and open pipe

Answer 21

f = nv/2L

Question 22

wavelength of a standing wave in a closed pipe

Answer 22

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

Question 23

frequency of a standing wave in a closed pipe

Answer 23

f = nv/4L

Question 24

ultrasound

Answer 24

• 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