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Physics A Level > Chapter 11 Waves 1 > Flashcards

Chapter 11 Waves 1 Flashcards

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1
Q

What are primary and secondary waves?

A

They are both forms of progressive waves

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2
Q

What is an S-wave?

A

A secondary wave that is transverse

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3
Q

What is a P-wave?

A

A primary wave that is longitudinal

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4
Q

What is a progressive wave?

A

It is a wave that moves through matter or a vacuum and It transfers energy without transferring matter.

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5
Q

What is an equilibrium position in terms of waves?

A

It is the position that particles are in when there is no wave passing through it. Any deviation from this position is a deviation from the equilibrium

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6
Q

What is a restoring force?

A

This is the force that a particle experiences when it is restored back to its original position

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7
Q

What is a transverse wave?

A

It is a wave that oscillates perpendicular to the direction of travel of the wave.

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8
Q

What are some examples of transverse waves?(4)

A

Waves on the surface of water
Any electromagnetic wave
Waves on a stretched string
Swaves produced by earthquakes

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9
Q

What is a peak and what is a trough?

A

These are both the maximum displacement of a particle from equilibrium. Peak is the positive displacement and a trough is the negative displacement

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10
Q

What is a longitudinal wave?

A

It is a wave that oscillates parallel to the direction that the waves travel

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11
Q

What are some examples of longitudinal waves?(2)

A

Sound

pwaves from earthquakes

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12
Q

What is a compression and a rarefaction?

A

A compression is an area of high pressure and a rarefaction is an area of low pressure

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13
Q

What is displacement?

A

It is the distance that a particle is from equilibirum

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14
Q

What is amplitude?

A

It is the maximum displacement from equilibrium

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15
Q

What is wavelength?

A

This is the minimum distance between two identical points on a wave

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16
Q

What is the period of oscillation?

A

This is the time it takes for one oscillation

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17
Q

What is the frequency?

A

It is the number of wavelengths passing a point in a second, also the number of oscillations per second

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18
Q

What is wave speed?

A

It is the distance travelled by a wave per unit of time

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19
Q

What is the wave equation?

A

V = Fλ

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20
Q

What is the equation to find frequency from time period?

A 
f = 1/t
f = frequency
t = timeperiod
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21
Q

What is phase difference?

A

it is Difference between the displacements of particles on a wave

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22
Q

What does in phase mean?

A

This is when particles are oscillating perfectly in step with each other. The reach there maximum displacements at the same time

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23
Q

What is the opposite of in phase and what does it mean?

A

Antiphase is when the particles are completely (180*) out of step and when one particle reaches it maximum positive displacement the other (equivalent) particle reaches its most negative displacement

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24
Q

What is a displacement-distance graph show?

A

It is a graph of the displacement per distance the wave has traveled. And it can also be interpreted as a snapshot of the wave. The wavelength can be calculated by measuring the distance between any two points on the graph

25
Q

What is a displacement-time graph?

A

It shows the displacement of a particle on a wave as time varies. The frequency can be worked out by counting the number of waves per interval of time (second)

26
Q

What is a reflection?

A

It is when a wave changes direction at a boundary between two different media whilst still remaining in the original medium

27
Q

What is the law of reflection?

A

The angle of incidence is equal to the angle of reflection

28
Q

How can light be represented?

A

It can be represented as a ray ( a straight line) or a wave front (perpendicular lines to the direction that the light moves)

29
Q

What is refraction?

A

This is when light changes the medium it flows through and due to the change in speed it changes direction

30
Q

What happens if the speed of the wave slows down when changing medium?

A

Refract towards the normal

31
Q

What happens if the speed of the wave increases when changing medium?

A

It refracts away from the normal

32
Q

What happens if a) light or b) sound enters a denser medium?

A

a) When light enters a denser medium it slows down

b) when sound enters a denser medium it speeds up

33
Q

What happens when light enters water from air?

A

It bends towards the normal and the wavelength gets smaller

34
Q

What is diffraction and what is the property unique to?

A

Diffraction is unique to waves and is when it spreads out as it passes through a gap

35
Q

What is polarisation? and plane polarisation?

A

This is when particles oscillate in a single direction. along a single plane

36
Q

What does unpolarised light look like?

A

It is light that oscillates in multiple directions.

37
Q

What does the amount of diffraction rely on?

A

It relies on the size of the gap that it passes through and the wavelength

38
Q

What does partial polarisation? and when does it happen?

A

This is when light oscillates in more than one plane but it not fully unpolarised. its sort of half way between
This happens when light reflects off a surface like a lake

39
Q

What is intensity and what is its equation and units?

A

It is the radiant power passing through a surface per unit of area.
I = P / A
Units: Wm^-2

40
Q

What is the equation for intensity from a sphere?

A

I = P / 4πr^2

41
Q

What happens to the intensity if the distance from a source doubles?what is the general equation

A

The intensity is 1/4

I ∝ 1/r^2

42
Q

How is amplitude and intensity related?

A

Intensity ∝ (amplitude)^2

43
Q

What is special about electromagnetic waves vs other waves?

A

It does not need a medium to pass through

44
Q

What is the order of the electromagnetic spectrum from large to small wavelength?

A 
Radio wave
Microwave
Infrared
Visible
Ultraviolet
Xray
Gamma Ray
45
Q

What is the wave equation for electromagnetic waves?

A

c = fλ

46
Q

What is the speed of light? and symbol?

A

c = 3x10^8

47
Q

What is a polarising filter and how does it work?

A

It is a filter that polarises light. It acts like a gate and so only the light that is oscillating with the direction of the rails is allowed through.
Light that oscillated differently is simply cut out

48
Q

What is a use for polarising filters and explain how this is usefull?

A

It is used for ariels where the wave is polarised to reduce interference between different transmitters.

49
Q

What is a refractive index?

A

This is a measure of how light bends when changing between mediums. Each medium is given a factor

50
Q

What is the equation for the refractive index?

A 
n = c / v
n = refractive index factor
c = speed of light in vacuum
v = speed of light in the medium
51
Q

What medium has a refractive index of 1?

A

A vacuum

52
Q

What is the refraction law equation?

A

n1Sinθ1 = n2Sinθ2
n1 is the refractive index of medium 1 and θ1 is the angle of incidence against the normal
n2 is the refractive index of medium 2 and θ2 is the angle of incidence against the normal

53
Q

What medium has the highest refractive index?

A

Diamond with an index of 2.42

54
Q

What is total internal reflection?

A

This is when light leaving a medium is at such an angle that when it strikes the boundary and reflects instead of refracts

55
Q

What are the two conditions of total internal reflection?

A

The light must be travelling from a medium of high refractive index towards one of low refractive index
The angle at which the light strikes the boundary must be above the critical angle

56
Q

What is the critical angle?

A

This is the smallest angle that produces a total internal reflection. It is dependent on the medium involved

57
Q

What is the equation for the critical angle?

A

Sinθ = 1 / n

n is the refractive index of the medium that the light is travelling through

58
Q

How can the refractive index be calculated?

A

A ray box is used to put light into a semicircular box and then the angle of incident is change with the ray box until it totally internally reflects at an angle of 90* to the normal. The angle between the incident light from the ray box and the normal is calculated. Then the equation Sin θ = 1 / n is used

Physics A Level (27 decks)

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