2.5 - Wave Motion and Sound

Question 1

What is the formula for time period?

Answer 1

T = 1/f

where

T = Time period

f = frequency

Question 2

What is the Doppler effect?

Answer 2

The Dopper effect (or the Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source

Question 3

What is the type of wave that moves parallel direction?

Answer 3

Longitudinal or compressed wave

'’Wave in which particles of the medium move in a direction parallel to the direction which the wave moves’’

Question 4

Give an example of a Longitudinal wave?

Answer 4

Sound wave

Question 5

What is the wave in which vibrations are perpendicular to the direciton of wave travel?

examples?

Answer 5

Transverse wave

'’Wave moves in a direction perpendicular to the direction which the wave moves’’

energy transported left to right and particles up and down

Transverse waves = light, radio waves, microwaves

Question 6

In terms of the Doppler effect, what happens when the source moves toward and away from observer?

Answer 6

If the source is moving towards the observer , the observer percieves sound waves reaching him or her at a more frequent rate (high pitch)

if the source is moving away from the observer, the observer percieves sound waves reaching him or her at a less frequent rate (low pitch)

Question 7

If the source is moving towards the observer , the observer percieves sound waves reaching him or her at _______________________

if the source is moving away from the observer, the observer percieves sound waves reaching him or her at ___________________

Answer 7

If the source is moving towards the observer , the observer percieves sound waves reaching him or her at a more frequent rate (high pitch)

if the source is moving away from the observer, the observer percieves sound waves reaching him or her at a less frequent rate (low pitch)

Question 8

Where is the position of the nodes and antinodes on a wave graph?

Answer 8

Antinodes at the top of each wave (A)

Nodes are at the 0 point, along the axis

Question 9

What would be positioned at the fixed end of a wave that is reflected?

(node or antinode)

Answer 9

node

(thus has to be antinode at the open end)

Question 10

Superposition of waves

What happens to a constructive wave?

Answer 10

When two peaks coincide, constructive waves occur that are at the same frequency will increase the amplitude

Question 11

Superposition of waves

What happens to a destructive wave?

Answer 11

When at the same frequency and a trough coincides with a peak

destrucive interference occurss (noise cancelling)

Question 12

What is a standing wave?

Answer 12

Standing or stationary wave is a wavve in which each point of the wave has an associated amplitude.

The locations at which the amplitude is minimum are called nodes and the locations where the amplitude is maximum are called antinodes

Question 13

What is the speed of sound in each of the following:

air @ 0^C =

air @ 20^C =

steel =

Answer 13

What is the speed of sound in each of the following:

air @ 0^C = 331 m/s

air @ 20^C = 344 m/s

steel = 5790 m/s

Question 14

What does the amplitude of a wave correspond to?

Answer 14

The greater the amplitude of a wave then the more energy it is carrying

(energy)

Question 16

What is timbre?

Answer 16

All objects have a natural frequency and the quality of this and musical instruments is defined as timbre

Question 17

Sound quality (tone) depends on

Answer 17

the mix of harmonics

Question 18

Sound waves are transferred through the air by:

a) electromagnetic waves
b) alternate low and high pressure air

Answer 18

b) alternate low and high pressure air

Question 19

Answer 19

Question 20

What is meant by the term resonance?

Answer 20

Resonance describes when a vibrating or external force drives another system to oscillate with greater amplitude at a specific pefererntial frequency.

Frequencies at which the response amplitude is a relative maximum are known as the system’s resonant frequencies or natural frequencies

Question 21

What is meant by beat frequency?

Answer 21

Suppose we tune two strings of a guitar to vibrate almost, but not quite, the same frequency.

Plucked simultaneously, the volume of the sound produced by them appears to rise and fall continuously.

This rise and fall has a fixed frequency called the beat frequency

What is happening is that the sound waves prodcued by the two guitar strings interfere and our ears detect the variation of the resultant intensity. Maximum intensity is heard when the waves add together (interfere constructively) and minimum intensity is heard when the waves cancel each other out (interfere destructively)

Question 22

In terms of a sound wave

The pitch corresponds to the ________

the loudness corresponds to the ______

Answer 22

The pitch corresponds to the frequency

the loudness corresponds to the amplitude

Question 23

which is high vs low frequency

Answer 23

Question 24

Rafeifraction is related to which type of wave?

Answer 24

Compression (longitudinal) wave

Question 25

What is the speed of sound in air at 0 ^C?

Answer 25

331 m/s

Question 26

Doubling of wavelengths results in ______________________

Answer 26

halving the frequency, but wave speed does not change

Question 27

A high pitch sound corresponds to a _____frequency and a low pitch sound corresponds to a _______ frequency

Answer 27

A high pitch sound corresponds to a high frequency and a low pitch sound corresponds to a low frequency

Question 28

When two waves interfere, the resulting displacement of the medium at any location is

Answer 28

the algebraic sum of the displacements of the individual waves at that same location

Question 29

When 2 waves of the same phase coincide, is it?

a) constructive
b) destructive

interference

Answer 29

a) constructive

Question 30

What is a standing wave?

Answer 30

Interference between a wave and its own rebound reflection creates a ‘standing wave’