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A Level Physics > C11/12 (Waves) > Flashcards

C11/12 (Waves) Flashcards

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1
Q

What’s meant by a progressive wave

A

Is a mean of transfering energy from one place to another without a transfer of matter between the two points

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2
Q

What are the two types of progressive waves

A

Transverse

Longitudinal

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3
Q

What do mechanical waves rely on to transfer energy?

A

Matter

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4
Q

Do EM waves rely on matter to transverse energy

A

No

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5
Q

Transverse waves (definition)

A

The direction of oscillation of a wave is perpendicular to the direction of motion of the wave

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6
Q

Transverse waves (examples)

A

Em waves (light and radio waves)
String waves
Seismic waves
Water waves

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7
Q

What are the troughs and peaks of a transverse wave?

A

The points where the oscillating particles are at a maximum displacement from their equilibrium position

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8
Q

Longitudinal waves (definition)

A

The direction of oscillation of a wave is parallel to the direction of motion of the wave

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9
Q

Longitudinal waves (examples)

A

Sound waves

P-waves

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10
Q

What is alternative name for longitudinal waves

A

Compression waves

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11
Q

What does a longitudinal wave consist of?

A

Areas of compression and refraction

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12
Q

S

Displacement

A

Units (m)

Distance from equilibrium position in a particular direction; a vector so can have a postive or negative value

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13
Q

A

Amplitude

A

Units (m)

Maximum displacement from the equilibrium position

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14
Q

Lambda

Wavelength

A

Units (m)

Minimum displacement between 2 points in phase on adjacent waves

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15
Q

T

Peroid of oscialltion

A

Units (s)

Time taken for one oscillation

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16
Q

f

Frequency

A

Units (Hz)

Number of wavelengths passing a given point per unit time

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17
Q

v or c

Wave speed

A

Units (m/s)

Distance travelled by the wave per unit time

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18
Q

What can a Displacement-Distance graph be used to find?

A

The amplitude and wavelength of both types of waves

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19
Q

What can a Displacement-Time graph be used to find?

A

Find the Time period, amplitude and frequency of both types of waves

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20
Q

The wave equation

A

Velocity= Frequency x Wavelength

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21
Q

What is the equation of wave speed, including time peroid?

A

Velocity= Wavelength / Time peroid

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22
Q

Equation for Frequency

A

Frequency = 1 / Time period

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23
Q

What does phase difference describe

A

The difference between the displacement or particles on a wave, or the difference between the displacement of particles on different waves.

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24
Q

What is phase difference measured in

A

Degrees or radians

Each complete wave as 360° or 2pie radians

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25
Q

When will particles reach max positive displacement at the same time

A

If particles oscillate perfectly in step with each other, both reach max positive displacement at the same time, they are described as in place. Phase difference of zero.

26
Q

If particles are separated by a whole wavelength we say

A

The phase difference is 360° or two pi radians.

27
Q

If two wavelengths out what is the phase difference

A

Phase difference is four pi radians or 720° etc

28
Q

Equation for phase difference

A

Phase difference equals distance divided by wavelength times by 360 for degrees or multiple by 2pi to get in radians

29
Q

When does reflection occur

A

When wave changes direction at the boundary between 2 different media, remaining in the original medium (light reflecting off a mirrored surface).The light waves remain in the original medium (the air)

30
Q

What does the rays of a diagram show

A

The rays direction of energy transfer and so the path taken by the wave

31
Q

When does the law of reflection apply

A

Whenever waves are reflected

32
Q

What does the law of reflection state

A

It states that the angle of incidence is equal to the angle of reflection

33
Q

When a wave is reflected what happens to the wavelength and its frequency

A

It’s remains unchanged

34
Q

When does refraction occur

A

Refraction occurs when a wave changes direction as it changes speed when it passes from one medium to another.

35
Q

Whenever a wave refracts, is there ever some sort of reflection off the surface?

A

There is always some reflection off the surface (partial reflection)

36
Q

In refraction if the wave slows down how will it refract?

A

It will refract towards the normal

37
Q

If a wave speeds up how will it refract

A

It’s refracts away from the normal

38
Q

Does refraction have an affect on the wavelength and frequency

A

Refraction has an affect on wavelength but not frequency. If a wave slows down its wavelength decreases and frequency remains unchanged and if a wave speed up its wavelength increases and frequency remains unchanged

39
Q

Refractive index equation

A

Refractive index equals speed of light in a vacuum divided by the speed of wave (varies)

40
Q

The greater the refractive index the more the light entering the material is…

A

Refracted towards the normal.

41
Q

Refraction of water waves

A

Speed of water waves affected by changes in the depth of the water (easy way to investigate refraction of water waves). When a wave enters shallow water, it slows down and the wavelength gets shorter.

42
Q

Diffraction

A

Is a property unique to waves.

When waves pass through a gap or travel around an obstacle, they spread out

43
Q

What waves can be diffracted

And what wave properties change

A

All waves can be diffracted

Speed wavelength and frequency all remain unchanged

44
Q

What determines how much a wave defracts

A

Depends on the relative sizes of the wavelength and the gap or obstacle

45
Q

When is diffraction most significant

A

It will only occur is the wavelength is similar to the size of the gap or obstacle (the more similar they are the significant the diffraction is).

46
Q

Polarisation

A

Polarisation means that the particles oscillate along one direction only, which means the wave is confined to a single plane.

47
Q

Unpolarised light

A

Light that oscillates in many different planes

48
Q

What type of waves can be polarised and why

A

Transverse only.
The particles in Longitudinal waves oscillation are always parallel to the direction of energy transfer, can’t be polarised. Their oscillation are already limited to only one plane (direction of energy transfer).

49
Q

Partial polarisation

A

When transverse waves reflect off a surface, become partially polarised. Meaning there are more waves oscillating in one particular plane, but wave isn’t completely polarised.

50
Q

Partial polarisation occurs on what type of surfaces

A

Non-metallic surfaces
Metallic surfaces reflect light with a variety of vibrational directions, such reflected light is unpolarized.

51
Q

Intensity

A

The radiant power passing through a surface per unit area,

Measured in Wm^2

52
Q

Equation for intensity

A

I= P/A

I= P/ 4 pi r^2

Where A is the surface area or a sphere

53
Q

Diffraction

A

The spreading of waves when they pass through a gap or by an edge/ obstacle

54
Q

Coherence

A

Two waves are said to be coherent if they have the same frequency and the same constant phase difference

55
Q

Incoherence

A

If two waves don’t have the same frequency or a constant phase difference

56
Q

Superposition

A

When two or more waves overlap, the resultant displacement at a point is equal to the sum of the individual displacement at that point

57
Q

Constructive interference

A

When the crests/ troughs of 2 waves coincide, they combine to create an amplified wave.
(The 2 waves are in phase with each other, zero phase difference).

58
Q

Destructive interference

A

Where the crests of one wave are aligned with the troughs of another, they cancel each other out (or lower ones amplitude).

The wave are out of phase (anti phase), have half a cycle difference from each other.

59
Q

What can an interference pattern be produced from?

A

2 coherent wave sources

60
Q

How to work out path difference

A

Measure distance of one source and the other (find difference)
(Should be a multiple of the wavelength)

61
Q

When do constructive interference occur?

A

Whenever the path difference between coherent sources is n x wavelength (where n is a whole number)

62
Q

When do destructive interferences occur?

A

When path difference between coherent sources is n x wavelength / 2
(n is a whole number)

A Level Physics (28 decks)

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