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A-Level Physics > [AS] Waves > Flashcards

[AS] Waves Flashcards

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1
Q

What is a wave

A

A wave is the oscillation of particles or fields

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2
Q

What is a progressive wave

A

A moving wave which carries energy from one place to another without transferring any material

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3
Q

A wave is caused by …

A

Something making particles or fields oscillate(vibrate) at a source

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4
Q

What is the displacement of a wave?

A

How far a point on the wave has moved from its undisturbed position

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5
Q

What is the amplitude of a wave?

A

Maximum magnitude of displacement

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6
Q

What is the frequency of a wave? What’s the equation?

A

The number of cycles that pass a given point per second

F= 1/T

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7
Q

What is meant by phase difference?

A

The amount one waves lags behind another

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8
Q

What is refraction?

A

The wave changes direction as it enters a different medium

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9
Q

What is a transverse wave?

A

Vibrate at right angles to the direction of energy transfer

E.g. all electromagnetic waves

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10
Q

What is a longitudinal wave?

A

Vibrate along the direction of energy transfer

E.g. sound

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11
Q

What is polarisation?

Examples?

A

The filtering of transverse waves into just one plane of motion

Tv and radio signals

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12
Q

Polarisation is evidence that …..

A

Electromagnetic waves are transverse

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13
Q

What is superposition?

A

2 or more waves pass through each other

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14
Q

What happens during constructive interference?

A

Crest meets crest
Or
Trough meets trough

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15
Q

What happens during destructive interference?

A

Crest and trough cancel out

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16
Q

How do 2 points in phase on a wave interfere?

A

Constructively

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17
Q

What is meant by in phase?

A

They are both at the same point in the wave cycle

Phase difference of zero or 360 etc

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18
Q

What is meant by 2 point exactly out of phase?

A

2 points with a phase difference of 180 degrees

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19
Q

To get interference patterns the two sources must be coherent.
What does this mean?

A

Same wave length and frequency

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20
Q

What is a stationary wave?

A

(Progressive wave reflected at a boundary)

The superposition of two progressive waves with the same frequency moving in opposite directors.

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21
Q

Is energy transmitted by a stationary wave?

A

Will Mike ever dunk?😂

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22
Q

How can you demonstrate a stationary wave?

A

Setting up a driving oscillator at one end of a stretched string with the other end fixed

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23
Q

What is meant by resonant frequent?

A

The frequency needed to create a stationary wave

24
Q

Do stationary on strings form oscillating loops?

A

Can Marcus dunk?🤗 (yes)

25
Q

what is diffraction?

A

waves spread out as they go round cornors or through a narrow gap

26
Q

when the gap is a lot bigger than the wavelength, diffraction is……

A

unnoticeable

27
Q

when do you get the most diffraction?

A

when the gap is the same size as the wave length

28
Q

what happens if the wavelength is much bigger the the gap?

A

mostly reflection

29
Q

what do you see when demonstrating diffraction patterns with a monochromatic, coherent light source?

A

a central fringe, with dark and bright fringes alternating on either side

30
Q

what do you see when demonstrating diffraction patterns with white light?

A

multicoloured fringes

31
Q

what does light intensity mean

A

the number of photons

32
Q

describe young double slit experiment in 3 points

A

shine a laser between 2 slits
slits need to be about the same size as the wavelength of the light
you get a pattern of light and dark fringes depending of whether there is constructive or destructive interference

33
Q

what was youngs double slit experiment evidence for?

A

the wave nature of EM radiation

34
Q

what happens the the interference patterns of waves when you increase the number of slits?

why?

A

they get sharper

there are more beams reinforcing the pattern

35
Q

dsinX = n(wavelength)

what does n, X and d mean?

A 
n = which order 
X = angle between zero order and n 
d = space between slits
36
Q

What is refractive index a measure of?

A

The ratio of the speed of light in two materials

37
Q

n = C/Cs

what does each letter mean?

A 
n= refractive index 
C= speed of light in a vacuum 
Cs= speed of light in material
38
Q

Where do you measure the angle of incidence between?

A

The incoming ray of light and the normal

39
Q

How does the angle of refraction change when light enters an optically denser medium?

A

Refracted towards the normal

40
Q

How does the angle of refraction change when light enters an optically less dense medium?

A

Refracted away from the normal

41
Q

At what angle is light refracted along the boundary when light enters an optically less medium?

A

Critical angle

42
Q

What happens when the angle of incidence is greater than the critical angle when entering an optically DENSER medium?

A

Nothing

43
Q

What happens when the angle of incidence is greater than the critical angle when entering an optically LESS DENSE medium?

A

Total internal reflection

44
Q

What must be true about the density of the materials for total internal reflection to happen?

A

The light enters an optically less dense medium

45
Q

What is the refractive index of optical fibres?

A

HIGH

46
Q

What is the refractive index of optical fibre cladding?

A

LOW

47
Q

How does light move through a optical fibre?

A

Total internal reflection

48
Q

How can signal degradation happen in an optical fibre?

A

Absorption, Dispersion

49
Q

What is signal degradation by absorption?

A

Some of the signal’s energy is lost through absorption by the material,
reducing its amplitude

50
Q

What is signal degradation by dispersion?

A

Signals disperse as they travel down the wire.

Broadened pulses overlap and interfere with each-other

51
Q

What are the two types of dispersion?

A

Modal, Material

52
Q

Describe modal dispersion

A

Light enters the wire at different angles, so they take different paths.

53
Q

Describe material dispersion

A

Light of different wavelengths travels at different speeds through the wire

54
Q

How can you prevent modal dispersion?

A

Using a “single-mode fibre”

55
Q

How can you prevent material dispersion?

A

Using monochromatic light

56
Q

How can you reduce signal degradation along an optical fibre?

A

An optical fibre repeater

boosts and regenerates the signal

A-Level Physics (13 decks)

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