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Physics STAGE 3 > Waves > Flashcards

Waves Flashcards

0
Q

What are the two types of mechanical waves

A

Longitutinal waves

Transverse waves

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1
Q

What is a wave

A

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

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2
Q

Mechanical waves

A

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

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3
Q

Longitutinal waves

A

Particles vibrate parallel to the direction of energy flow

Examples: earthquake P waves, sound waves

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4
Q

Transverse waves

A

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

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5
Q

Describe field of Electromagnetic waves

A

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

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6
Q

Properties of electromagnetic waves

A

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

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7
Q

How can astronauts communicate with each other in space

A

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

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8
Q

Displacement of medium

A

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

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9
Q

Distance in a water wave

A

The position of the particle on the after surface

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10
Q

Compression

A

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

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11
Q

Rarefaction

A

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

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12
Q

Vibration

A

A to and fro motion (back and forth)

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13
Q

Cycle

A

One complete vibration

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14
Q

Period

A

Symbol T
Time for one complete vibration
Units in seconds

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15
Q

Frequency

A

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

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16
Q

Human ears can hear up to what frequency?

A

20-20 000Hz

It is called the audible range

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17
Q

Amplitude

A

Symbol A

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

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18
Q

Relationship between amplitude and energy of a wave

A

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

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

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19
Q

Wavelength

A

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 )

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20
Q

Velocity

A

Symbol V or c

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

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21
Q

What determines a wave’s speed

A

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

22
Q

Phase

A

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

23
Q

Ray

A

A directed line showing the direction of propagation of a wave

24
Q

Wavefront

A

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

25
Q

Relationship of speed of sound in solids, liquids and gases

A

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

26
Q

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

A

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

27
Q

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

A

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.

28
Q

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

A

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

29
Q

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

A

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

30
Q

Pitch

A

A position on a musical scale

It is related to frequency

31
Q

Low pitch

A

Deep or bass sounds

32
Q

High pitch

A

High or treble sounds

33
Q

Relationship between frequency and pitch

A

Higher frequency, higher pitch

34
Q

Loudness

A

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

35
Q

Relationship between amplitude and loudness

A

Higher amplitude, higher loudness

36
Q

Relationship of Increase in decibels to amount of energy

A

Increase in 3dB implied twice the amount of energy

37
Q

What does quality do?

A

Gives each instrument it’s characteristic sound

38
Q

What does quality depend on ?

A

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

39
Q

How do you differentiate between noise and music?

A

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

40
Q

Reflection

A

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

41
Q

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

A

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

42
Q

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

A

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

43
Q

Law of reflection

A

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

44
Q

What makes a good reflector of light?

A

A shiny, smooth surface

45
Q

Regular reflection

A

Occurs when parallel beam of incident rays remain parallel after reflection

Such as on smooth surfaces like a mirror

46
Q

Irregular reflection

A

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 )

47
Q

As a sound wave travels between materials it can be

A

Reflected, transmitted (diffused) or absorbed

48
Q

What are the properties of good sound reflectors

A

Smooth, hard surfaces

49
Q

What is an echo

A

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

50
Q

Conditions for an echo to happen

A

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

51
Q

Echoes can be produced by

A

Sound reflected from buildings, hills and cliffs

52
Q

Reverberation

A

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

53
Q

Conditions needed for reverberation

A

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

Physics STAGE 3 (1 decks)

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