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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

Define a mechanical wave

A

Involves motion of matter through vibrations of particles, ex sound waves, s & p waves

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2
Q

Define an electromagnetic wave

A

Vibrating electric and magnetic fields that can travel through a vacuum

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3
Q

What is energy proportional to?

A

Frequency

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4
Q

Define progressive waves

A

Waves that move outward from their source

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5
Q

Give another name for progressive waves

A

Travelling waves

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6
Q

What does the distance between two peaks represent on a displacement-distance graph?

A

Wavelength

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7
Q

What does the distance between two peaks represent on a displacement-time graph represent?

A

The time period

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8
Q

Define amplitude

A

The maximum displacement of the wave or medium from the equilibrium position

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9
Q

Define wavelength

A

The horizontal distance between two crests or two troughs

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10
Q

Define time period

A

The time taken for a wave peak to travel the distance of one wavelength

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11
Q

Define frequency

A

The number of waves passing a point per unit time.

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12
Q

Give the unit of frequency

A

S to the -1 (‘per second’)

This is more commonly called Hz (Hertz)

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13
Q

Give the symbol for radians in physics

A

rad

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14
Q

Define two waves that are in phase

A

They are always in the same place on the wave cycle

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15
Q

Define two waves in antiphase

A

They are 180 degrees apart; they have an exactly opposite pattern of oscillation

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16
Q

Define longitudinal waves

A

Each particles oscillates parallel to the direction of energy transfer. There is no vertical movement.

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17
Q

Define transverse waves

A

Each particles oscillates perpendicular to the direction of energy transfer. There is no horizontal movement.

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18
Q

Are S waves longitudinal or transverse?

A

Transverse

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19
Q

Are water waves longitudinal or transverse?

A

Transverse

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20
Q

Are p waves longitudinal or transverse?

A

Longitudinal

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21
Q

Is it rarefraction or rarefaction?

A

Rarefaction!

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22
Q

What is significant about the speed of electromagnetic waves in a vacuum?

A

They’re all the same speed

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23
Q

Which type of wave can be polarised?

A

Transverse waves

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24
Q

Define polarised

A

All oscillations are in one plane

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25
Q

Define unpolarised

A

Oscillations are in all planes

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26
Q

What are the methods got polarising visible light?

A

A polarising filter
Reflection
Scattering

27
Q

Which ray is polarised when light hits a transparent object (such as glass or water)?

A

The reflected Ray

28
Q

What is significant about polarisation through reflection?

A

The light will only be partially polarised.

At an angle specific to the material the light will all be polarised

29
Q

What is the axis of transmission?

A

The plane the electric field is oscillating in after polarisation

30
Q

How is polarisation used in stress analysis?

A

In transparent plastics, areas of high stress polarise light in different directions to areas of low stress

31
Q

Give two uses of polarisers

A

Polaroid material

Aerials for transmission and reception

32
Q

Define superposition

A

When two or more waves of the same type meet at a point, the resultant displacement of the oscillations will be the vector sum of the individual displacements.

33
Q

Define constructive interference

A

If both waves have the same sign displacement at the point of overlap
(ie both negative or both positive)

34
Q

Define destructive interference

A

If one wave has a positive displacement and the other has a negative displacement at the point of overlap

35
Q

Give another name for standing waves

A

Stationary waves

36
Q

Explain standing waves

A

The superposition of 2 progressive waves travelling in opposite directions can produce a standing wave.
The waves should be the same type, and have the same amplitude and frequency

37
Q

What happens at a node?

A

At a node on a standing wave no oscillations occur; the ends are fixed

38
Q

What happens at an antinode?

A

At an antinode on a standing wave, maximum oscillations occur

39
Q

Amplitude is the same for all points on a progressive wave. Is this also true for a standing wave?

A

No.

Different points on a standing wave have different maximum displacements.

40
Q

In a progressive wave, points on the same wave are not in phase with each other. Is this true for standing waves?

A

No - points on the same half of a wave are all in phase with each other; points at opposite halves of a wave are in antiphase with each other.

41
Q

How is energy transferred through a standing wave?

A

It is stored in the wave

42
Q

How can you calculate tension in a string for use in the first harmonic equation?

A 
T = mg
(Tension = mass * gravitational field strength)
43
Q

What does mu represent in the 1st harmonic equation?

A

Mass per unit length

Mass / length of string

44
Q

What is significant about the open ends in a wind instrument?

A

Open ends ALWAYS have an anti-node

45
Q

How can you tell a wave is the first harmonic?

A

It has 1 node and 2 antinodes

46
Q

Define coherent waves

A

Waves with a fixed phase difference and the same wavelength and frequency

47
Q

What is the approximate refractive index of air?

A

1

48
Q

In the refractive index equation, what does c equal?

A

The speed of light in a vacuum/ the speed of light in the substance

49
Q

What is the function of the cladding in a fibre optical cable?

A

To stop light passing from one fibre to another; to reduce light loss from the core.

50
Q

Define modal dispersion

A

The lengthening of a light pulse as it travels along an optical fibre, due to rays that undergo less total internal reflection

51
Q

Give another term form modal dispersion

A

Multi path dispersion

52
Q

What is material dispersion?

A

Modal dispersion that occurs if white light is used instead of monochromatic light because of the different wavelengths

53
Q

What does s stand for in the fringe spacing equation?

A

Slit spacing

54
Q

What does W stand for in the fringe spacing equation?

A

Fringe width

55
Q

What does D stand for in the fringe spacing equation?

A

Distance from slits to screen

56
Q

Describe the interference pattern of white light is used in Young’s double slit experiment

A

The central fringe will be white and the others are a spectrum of colours
Violet on the inside
Fringes overlap because they are wider than monochromatic fringes

57
Q

Describe the diffraction pattern from a single split

A

Central maxima twice as wide as other fringes
Central maxima brighter than other fringes
Pattern becomes more spread out if a narrower slit or larger wavelength are used

58
Q

Describe the effect on the diffraction pattern of the slit is made narrower

A

Fringe separation larger

Brightness reduces as less light allowed through

59
Q

Describe the effect on the interference pattern of green light is used instead of red

A

Fringe separation smaller

60
Q

What’s the differences between a single and double slit interference pattern?

A

Single:
Central fringe very bright
Central fringe twice as wide as others
Double: all fringes similar brightness and width

61
Q

In the diffraction grating equation what does n stand for?

A

The order of the fringe

62
Q

In the diffraction grating equation what does theta represent?

A

Angle between fringe and n=0 central line

63
Q

In the diffraction grating equation what does d stand for and how do you calculate it?

A 
Slit separation (in lines per mm)
Do 1m divided by the number of lines per metre

Physics (2 decks)

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