Waves and sound

Question 1

Transverse waves

Answer 1

have oscillations of wave particles, perpendicular to the direction of wave propagation

Question 2

Longitudinal waves

Answer 2

have oscillations of wave particles parallel to the direction of wave propagation

Question 3

Displacement (x)

Answer 3

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

Question 4

amplitude (A)

Answer 4

of wave is the magnitude of its maximal displacement

Question 5

crest

Answer 5

max point of a wave ( point of most positive displacement)

Question 6

trough

Answer 6

minimum point of a wave (point of most negative displacement)

Question 7

Wavelength (λ)

Answer 7

the distance between two crests or troughs

Question 8

frequency (f)

Answer 8

the number of cycles it makes per second. It is expressed in hertz (Hz)

Question 9

Angular frequency (w)

Answer 9

another way of expressing frequency and is expressed in radians per second
w = 2πf = 2π/T

Question 10

Period (T)

Answer 10

the number of seconds it takes to complete a cycle. It is inverse of frequency . T = 1/f

Question 11

Interference

Answer 11

the ways in which waves interact in space to form resultant wave.

Question 12

Constructive interference

Answer 12

occur when waves are exactly in phase with each other. The amplitude of the resultant wave is equal to the sum of the amplitudes of the two interfering waves .

Question 13

Destructive interference

Answer 13

occurs when waves are exactly out of phase with each other. The amplitude of the resultant wave is equal to the difference in amplitude between the two interfering waves.

Question 14

Partially constructive and partially destructive interference

Answer 14

occur when two waves are not quite perfectly in or out of phase with each other. the displacement of the resultant wave is equal to the sum of the displacements of the two interfering waves.

Question 15

Traveling waves

Answer 15

have continuously shifting points of maximum and minimum displacement

Question 16

Standing waves

Answer 16

produced by the constructive and destructive interference of two waves of the sam frequency traveling in opposite direction in the same space.

Question 17

antinodes

Answer 17

points of maximum oscillation

Question 18

Resonance

Answer 18

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

Question 19

Damping

Answer 19

decrease in amplitude caused by an applied or nonconservative force

Question 20

Sound

Answer 20

produced by a mechanical disturbance of a material that creates an oscillation of molecules in the material . Propagates through all forms of matter (but no a vacuum). With a medium, density increases, the speed of sound decreases

Question 21

The pitch

Answer 21

sound is related to its frequency

Question 22

Doppler effect

Answer 22

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. When source and detector are moving toward each other the apparent frequency will be higher than the emitted. When they are moving away the apparent will be lower. If the two objects are moving in the same direction, they can be high, lower, or equal depending on speed. When the source is move at or above the speed of sound, sonic booms or shock waves can form.
f’ =f (v+- vD)/(v-+vs)

Question 23

sound level

Answer 23

loudness or volume of sound. Related to intensity. Intensity is related to a wave’s amplitude. Intensity decreases over distance and some energy is lost to attenuation (damping) from frictional forces.
B = 10 log I/Io

Question 24

What can support standing waves?

Answer 24

open pipes and strings, the length of the string or pupe is equal to some or multiple of half wave-lengths.

Question 25

wave speed

Answer 25

v=fλ

Question 26

intensity

Answer 26

I = P/A

Question 27

change in sound level

Answer 27

Bf = Bi + 10 og If/Ii .

Question 28

wavelength of standing waves (strings and open pipes)

Answer 28

λ = 2L/n

Question 29

Frequency of a standing wave (strings and open pipes)

Answer 29

f =nv/2L

Question 30

Wavelength of a standing wave (closed pipes)

Answer 30

λ = 4L/n

Question 31

Frequency of a standing wave (closed pipes)

Answer 31

f = nv/4L