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AS Physics > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

What is refraction?

A

The bending of light at a surface/boundary because it has changed speed

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2
Q

Define a ray

A

Straight line showing direction of wave (energy direction). Should have an arrow

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3
Q

Define a beam

A

Multiple rays

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4
Q

Define a wavefront

A

A line joining all points that are in the same phase. Can be in any shape

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5
Q

What is true about a wavefront and an associated ray?

A

They are always perpendicular to each other

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6
Q

When looking at an axis, how do you measure all angles? (incidence, reflection etc.)

A

Between the ray and the normal

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7
Q

When does a wave not bend when it hits a surface and what happens instead?

A

When it hits the surface at 90 degrees. It only changes speed but carries on in a straight line

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8
Q

What happens to light when it goes from a less optically dense medium to a more optically dense medium?

A

The light will slow down and bend towards the normal

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9
Q

What happens to light when it goes from a more optically dense medium to a less optically dense medium?

A

The light will speed up and bend away from the normal

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10
Q

When drawing a refraction diagram, what must you always show regarding the incident ray?

A

Partial reflection

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11
Q

What happens if the boundaries that light enters are parallel in terms of the incident and emergent ray?

A

The incident ray will be parallel to the emergent ray

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12
Q

List the order of the spectrum

A 
Red
Orange
Yellow
Green
Blue
Indigo
Violet
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13
Q

Which colour of white light bends the best and why?

A

Blue as it has the largest refractive index

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14
Q

What is the first criteria that must be met for TIR to occur?

A

n of material light is moving from must be > n of material light is moving into

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15
Q

What is the second criteria that must be met for TIR to occur?

A

Angle i > critical angle at that boundary

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16
Q

What are optical fibres used for (2 uses)

A

Communications - Send enclosed signals down fibre optics

Endoscopes - Medical internal examination

17
Q

In optical fibres, why do you need fibres?

A

So that you can bend the tube

18
Q

With the image channel in an optical fibre, what must happen in terms of the bundle?

A

It must be coherent so the image comes out correctly/ have same relative position

19
Q

In fibre optics, what are the 2 components of it?

A

Core and cladding

20
Q

Why does a fibre optic need cladding?

A
  • Stop interference (signal leakage) between adjacent fibres
  • If there are abrasions/cuts/scratches, it would touch the cladding not the signal meaning the signal wouldn’t be weakened
21
Q

What is model dispersion?

A

When beams of light follow different paths down a fibre, so have different path lengths and the signal gets spread out

22
Q

What is the solution to model dispersion?

A

Make the core narrower and reduce the amount the pulses spread out.

23
Q

How can you make the core narrower in order to solve model dispersion?

A

With the cladding, otherwise the core would become narrow and brittle

24
Q

What is material dispersion?

A

When you send white light down a fibre optic and it spreads out.

25
Q

Why does material dispersion occur?

A

Because white light is made up of different frequencies /wavelengths. So they travel at different speeds

26
Q

What is the solution to material dispersion?

A

Use lasers/single frequency so the pulses don’t smear out

27
Q

Why is light given off a material (e.g sun)?

A

Because of the incandescence (giving off) of the material. This is because the material is hot

28
Q

What type of light in terms of spectrum is given off by the sun?

A

The light produced is a continuous spectrum

29
Q

What type of light in terms of spectrum is given off by a fluorescent tube?

A

The light given off comprises of blocks/bunches of frequencies

30
Q

What type of effect is diffraction?

A

An edge effect

31
Q

Why does diffraction occur?

A

Because waves interfere with themselves

32
Q

What is the main application of diffraction gratings?

A

Spectrometers

33
Q

How do spectrometers work?

A

The grating breaks up white light into a spectrum. Because of the first order line which is different for every wavelength.

34
Q

What 2 types of spectra would be observed in a spectrometer?

A

Continuous or emission

35
Q

What is a continuous spectrum?

A

A spectrum consisting of many different colours and wavelengths, but no gaps

36
Q

What is an emission spectrum?

A

Where energy levels change due to electrons de exciting and exciting.

37
Q

What happens when an electron de excites?

A

It gives off photons

38
Q

What can the absorption spectra be used to do in terms of stars?

A

Identify elements in stars

39
Q

Diagrams to look at:

A 
Young's double slits 
Double slits (young's slits)
Spectra and diffraction

AS Physics (12 decks)

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