3.3.2.3 - Refraction At A Plane Surface Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Refractive index of a material =

A

C / Cs (speed of light/speed of light in that material)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the refractive index of air?

A

1.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is snell’s law?

A

n1 sin 01 = n2 sin 02

n = refractive index.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What causes light to be refracted along the boundary?

A

When light is reflected at the critical angle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What causes light to be totally internally reflected?

A

When the angle is greater than the critical angle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What values can sin take?

A

Smaller than 1.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Sin c =

A

1/ refractive index

n2 / n1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are optical fibres used for?

A

To carry signals over long distances and round corners.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is cladding needed for optical fibres?

A

Optical fibres themselves have a high refractive index but are surrounded by cladding with a lower refractive index to allow total internal reflection. Moreover cladding protects the fibre from scratches which could let light escape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why is the fibre narrow?

A

So that light always hits the boundary between the fibre and cladding at an angle bigger than the critical angle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What two things cause signal degradation?

A

Absorption and dispersion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does absorption cause?

A

Loss in amplitude.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is absorption caused?

A

As signal travels, some of its energy is lost through absorption by the material the fibre is made from.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does dispersion cause?

A

Pulse broadening.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the two types of dispersion?

A

Modal and material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does Modal dispersion occur?

A

Light rays enter the fibre at different angles, and so take different paths. The rays which take a longer path take longer to reach the other end than those that travel down the middle of the fibre.

17
Q

How and why can modal dispersion be stopped?

A

A single-mode fibre only lets light take one path, so it stops modal dispersion.

18
Q

What causes material dispersion?

A

As light consists of different wavelengths that travel at different speeds in the fibre, this causes some light wavelengths to reach the nod of the fibre faster than others.

19
Q

What can stop material dispersion?

A

Using monochromatic light.

20
Q

Why is pulse broadening a problem?

A

Broadened signals can overlap each other and confuse the signal.

21
Q

What can be used to reduce both signal absorption and dispersion?

A

An optical fibre repeater can be used to boost and regenerate the signal every so often.