# Light Review

Light Review
1 / 31
Slide 1: Slide
PhysicsSecondary Education

This lesson contains 31 slides, with interactive quizzes, text slides and 1 video.

## Items in this lesson

Light Review

#### Slide 1 -Slide

what is refraction?

#### Slide 2 -Open question

Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Law of Reflection
Angle of incidence = Angle of reflection

#### Slide 3 -Slide

i
Angle of incidence
Incident ray
Refracted ray
Normal
Angle of incidence
Angle of refraction
r
Angle of refraction
Snell's Law
n = sin i / sin r

#### Slide 4 -Slide

But why does the light change direction when it goes into the glass block?

And then again when it leaves?

#### Slide 6 -Video

If the ray of light hits the block at an angle, the side that hits first is slowed down and so the ray starts to bend towards the normal. It has been refracted.

If the ray of light hits the block at an angle, the side that hits first is slowed down and so the ray starts to bend towards the normal. It has been refracted.
When it leaves the block, it speeds back up and so bends away from the normal.

#### Slide 7 -Slide

Refractive Index
• Refractive index measures the effect a medium has on light.
• The greater the refractive index, the greater the change in speed and direction.
• The refractive index is always a value greater than, or equal to, 1.
• The refractive indices of a vacuum and air are 1.

#### Slide 8 -Slide

Absolute Refractive Indices
Material
Refractive Index, n
glass
1.5
perspex
1.47
water
1.33
diamond
2.4

#### Slide 9 -Slide

Refractive Index
We calculate refractive index using Snell's Law:

where n = refractive index
i = angle of incidence
r = angle of refraction

#### Slide 10 -Slide

Calculating n
Use the information in the diagram to calculate the refractive index of paraffin wax.
Solution
n = sin i / sin r = sin(34) / sin(23)
n = 1.43

#### Slide 11 -Slide

Calculating an angle
Use the information in the diagram to calculate angle X.
Solution
n = sin i / sin r
We want r, so rearrange:
sin r = sin i / n = sin(20)/1.47
r = sin^-1(0.23) = 13.5 degrees

#### Slide 12 -Slide

A ray of red light is incident on one side of a glass prism in air.
The angle of incidence is 53° and the angle of refraction in the glass is 30°.
Calculate the refractive index.

#### Slide 13 -Open question

Solution taken from a mark scheme

#### Slide 14 -Slide

The diagram shows the wavefronts and the direction of travel of light in air.
The light travels more slowly in the transparent solid.
The refractive index of the transparent solid is 1.3.
The light is incident on the surface of the solid at an angle of incidence of 67°.
Calculate the angle of refraction of the light in the solid.

#### Slide 15 -Open question

The background, through the glass of water, appears distorted which means changed to be _______
A
clearer
B
less clear
C
transparent

#### Slide 16 -Quiz

The background through the glass of water appears distorted because of ____________.
A
reflection
B
refraction

#### Slide 17 -Quiz

The light ___________when it passes from air into glass or water.
A
slows down
B
speeds up
C
remain constant

#### Slide 18 -Quiz

The material that light passes through is called a __________.
A
medium
B
opaque
C
ray

#### Slide 19 -Quiz

Light passing from one medium to another causes it to change ___________.
A
direction
B
force
C
distance
D
energy

#### Slide 20 -Quiz

Which is NOT an example of a medium?
A
air
B
glass
C
water
D
wood

#### Slide 21 -Quiz

You will remember that light travels 'very fast'. The speed of light in air is __________ kilometres per second.
A
30
B
30 000
C
300 000
D
300 000 000

#### Slide 22 -Quiz

When light passes from air into water or glass, the light travels ________.
A
slower
B
faster
C
at the same speed
D
at 0 m/s

#### Slide 23 -Quiz

The light passing from air into glass or water is bent _________ the normal.
A
away
B
under
C
across
D
towards

#### Slide 24 -Quiz

When light passes from air into glass or water, the angle of incidence is ________ than the angle of refraction.
A
lesser
B
the same
C
greater
D
more constant

#### Slide 25 -Quiz

Both of incident and refracted angles are measured from the __________.
A
normal
B
boundary
C
air
D
water

#### Slide 26 -Quiz

The light _________ when it passes from glass or water into air.
A
slows down
B
speeds up
C
remains the same
D
disappears

#### Slide 27 -Quiz

We say that the light passing from glass or water into air is bent _______ from the normal.
A
towards
B
across
C
away
D
the same

#### Slide 28 -Quiz

When light passes from glass or water into air, the angle of incidence is ________ than the angle of refraction.
A
lesser
B
the same
C
greater
D
more constant

#### Slide 29 -Quiz

The change of speed can cause the light to change ___________.
A
its speed
B
its direction
C
distance

#### Slide 30 -Quiz

____________ of light is defined as the change in direction of light on passing from one medium to another because of change in speed.
A
Reflection
B
Diffraction
C
Refraction