Waves

Question 0

What are the two types of mechanical waves

Answer 0

Longitutinal waves

Transverse waves

Question 1

What is a wave

Answer 1

A wave is a periodic (repeating) disturbance which provides a method for the transfer of energy from one point to another without the physical transfer of matter

Question 2

Mechanical waves

Answer 2

Require a medium in which to propagate
Because it involves the transfer of vibrational energy between particles
Example: sound waves, water waves

Question 3

Longitutinal waves

Answer 3

Particles vibrate parallel to the direction of energy flow

Examples: earthquake P waves, sound waves

Question 4

Transverse waves

Answer 4

Particles vibrate in a direction perpendicular to the direction of energy flow
Examples: water waves, string waves, earthquake S waves

Question 5

Describe field of Electromagnetic waves

Answer 5

Consists of oscillating electric and magnetic fields that are perpendicular to the direction of wave travel

Question 6

Properties of electromagnetic waves

Answer 6

Can travel in a vacuum with a speed of 3x10^8 m/s
Does not require a medium
Electromagnetic waves can be considered to be transverse because the electric and magnetic fields move perpendicular to the direction of wave travel

Question 7

How can astronauts communicate with each other in space

Answer 7

Through the use of radio waves
Because they do not require a medium to travel
and can travel through a vacuum (space)
unlike sound waves

Question 8

Displacement of medium

Answer 8

The distance the particle has shifted from its normal (rest) position

Question 9

Distance in a water wave

Answer 9

The position of the particle on the after surface

Question 10

Compression

Answer 10

Where the particles are closer than normal, the pressure is higher than normal

Question 11

Rarefaction

Answer 11

When he particles are further apart than normal, the pressure is lower

Question 12

Vibration

Answer 12

A to and fro motion (back and forth)

Question 13

Cycle

Answer 13

One complete vibration

Question 14

Period

Answer 14

Symbol T
Time for one complete vibration
Units in seconds

Question 15

Frequency

Answer 15

The number of complete waves, vibrations or cycles per second .
Symbol f
Units are in hertz (Hz)

Question 16

Human ears can hear up to what frequency?

Answer 16

20-20 000Hz

It is called the audible range

Question 17

Amplitude

Answer 17

Symbol A

The size of the maximum particle displacement of a vibrating particle from its mean or equilibrium position

Question 18

Relationship between amplitude and energy of a wave

Answer 18

High amplitude = high energy wave
Low amplitude = low energy wave

Amplitude of a wave is related to the energy which it transports

Question 19

Wavelength

Answer 19

Symbol lamda
Distance between two adjacent points in phase
Units in metres

or

The distance the wave travels while a particle makes one complete vibration (that is in a period )

Question 20

Velocity

Answer 20

Symbol V or c

Distance covered by a wave per unit time (NOT the particle)

Question 21

What determines a wave’s speed

Answer 21

It is the nature of the medium (particle spacing, particle size, temperature, density) that determines the wave speed

Question 22

Phase

Answer 22

Symbol phi
The position and motion of a particle at any instant
Particles having the same displacement from their mean position and moving in the same direction are in phase

Question 23

Ray

Answer 23

A directed line showing the direction of propagation of a wave

Question 24

Wavefront

Answer 24

Line along crests of progressive waves Or A line in the path of wave motion on which disturbances at every point have the same hose

Question 25

Relationship of speed of sound in solids, liquids and gases

Answer 25

Particles in solids and liquids are closely packed and the vibrations (compressions and rarefactions ) are transmitted more easily in solids and liquids than in gases Speed of sound in gases < speed in liquids < speed in solids

Question 26

What happens when a sound wave passes from one medium to another?

Answer 26

The speed of the wave changes The wave length also changes frequency remains CONSTANT

Question 27

Why does the frequency remain constant as a sound wave travels from one medium to another?

Answer 27

Because at the interface (a point where 2 subjects meet and interact), the particles will still bump into each other the same number of times per second.

Question 28

Why does the wavelength and hence speed change as a sound wave travels from one medium to another?

Answer 28

Because the particles will be displaced though a different distance in a second medium and the second medium has different properties (eg. Density)

Question 29

What happens to a wave when the temperature of air increases ?

Answer 29

The speed of sound increases A higher temperature means that the air particles are moving faster (higher Ek) so the transmission of sound from one particle to the next is faster

Question 30

Pitch

Answer 30

A position on a musical scale | It is related to frequency

Question 31

Low pitch

Answer 31

Deep or bass sounds

Question 32

High pitch

Answer 32

High or treble sounds

Question 33

Relationship between frequency and pitch

Answer 33

Higher frequency, higher pitch

Question 34

Loudness

Answer 34

The degree of sensation given to a listener' sears It is related to the sounds amplitude (or intensity) Measured in dB decibels

Question 35

Relationship between amplitude and loudness

Answer 35

Higher amplitude, higher loudness

Question 36

Relationship of Increase in decibels to amount of energy

Answer 36

Increase in 3dB implied twice the amount of energy

Question 37

What does quality do?

Answer 37

Gives each instrument it's characteristic sound

Question 38

What does quality depend on ?

Answer 38

The instrument's shape, structure and material from which it is made These factors affect the harmonics played and their loudness

Question 39

How do you differentiate between noise and music?

Answer 39

Music or pleasant sounds are characterised by a wave pattern that regularly repeats, whereas Noises are characterised by random wave patterns that do not repeat

Question 40

Reflection

Answer 40

Reflection is the rebounding of a wave as it hits a new medium or material

Question 41

Describe what would happen is parallel rays of light strike a concave mirror? And how it could change as it curves more

Answer 41

Concave mirrors converters the light rays They are then reflected through a point called the focal point The curvier, the closer the focal point

Question 42

Describe what would happen is parallel rays of light strike a convex mirror? And how it could change as it curves more

Answer 42

Convex mirrors diverge (spread) the light rays The light rays are reflected outwardly The curvier the mirror, the further apart the light rays diverge

Question 43

Law of reflection

Answer 43

The angle of incidence (I) is equal to the angle of reflection (r)

Question 44

What makes a good reflector of light?

Answer 44

A shiny, smooth surface

Question 45

Regular reflection

Answer 45

Occurs when parallel beam of incident rays remain parallel after reflection Such as on smooth surfaces like a mirror

Question 46

Irregular reflection

Answer 46

Occurs when parallel beam of incident rays reflect in what seems to be unpredictable reflections Such as on rough surfaces like water ( rough - outer sea )

Question 47

As a sound wave travels between materials it can be

Answer 47

Reflected, transmitted (diffused) or absorbed

Question 48

What are the properties of good sound reflectors

Answer 48

Smooth, hard surfaces

Question 49

What is an echo

Answer 49

The reflection of sound that is heard separately from the original sound

Question 50

Conditions for an echo to happen

Answer 50

There needs to be an time interval of at least 0.1 seconds between the arrival of the original sound and the reflected sound for an echo to be heard

Question 51

Echoes can be produced by

Answer 51

Sound reflected from buildings, hills and cliffs

Question 52

Reverberation

Answer 52

Collection of the multiple reflections of sounds that combine to produce a louder richer sound

Question 53

Conditions needed for reverberation

Answer 53

The reflected sound waves have to reach your ear in less than 0.1 seconds after the original sound