Refraction of light. 1John says, ‘When hunting a fish under water, you should aim your spear...

Refraction of light

1 John says,

‘ When hunting a fish under water, you should aim your spear directly at the fish.’

Do you agree?

Yes, of course.

No, because the fish is actually located somewhere else.

No, because size of objects changes when they are put under water.

2 When sunlight falls on the water surface, which of the following occur(s)?

It is reflected back to the air.

It refracts into the water.

It is absorbed by water and turned into heat.

airglass

Refraction is the bending of light

when the light passes from one medium to another.

Introduction

airglass

Useful words to describe refraction of light

normal

incident ray

angle of refraction

angle of incidence

refracted ray

Introduction

airglass

• e.g. from air to glass

• Light is bent towards the normal.

incident raynormal

refracted ray

From a less dense to a denser medium

Introduction

airwater

From a denser to a less dense medium

• e.g. from water to air

• Light is bent away from the normal.

incident rayrefracted ray

normal

Introduction

Material Refractive index

Glass 1.5 – 1.7

Water 1.33

Perspex 1.5

Diamond 2.42

Refractive indices of some materialsRefractive index

airwater

Example 3A ray of light passes from air into water.Angle of incidence = 30

What is angle of refraction in water?nwater = 1.33

30

Q1 A boy shines a torch under…A boy shines a torch under water as shown.

Which one shows the correct path of the light ray?

A Path X.B Path Y.

C Path Z.

D All of them.

Q5 Statements:...

1st statement 2nd statementLight is bent towards the normal when it passes from air to glass.

Glass has a greater refractive index than air.

true? true? true? true?

YesYes YesYes

4 Examples of refraction of light

a Bent chopstick

• The chopstick appears bent because of refraction

4 Examples of refraction of light

b Shallower in water• The depth that the object is

actually at is called the real depth.

O

Ireal dept

h

Simulation

4 Examples of refraction of light

c Flickering objects in hot air

• The object you see through the unstable hot air appears blurred and flickering.

Q1 True or false: Light slows…

True or false: Light slows down when it enters a material from air.

(T/F)

Q2 True or false: The refractive…

True or false: The refractive index cannot be smaller than 1.

(T/F)

Q3 True or false: If light travel…

True or false: If light travel at the same speed in all materials, refraction would still occur when it passes from air to water.

(T/F)

Q4 True or false: If the speed of…

True or false: If the speed of light in raindrop is equal to that in air, there would be no rainbows. (T/F)

Q5 Sketch a ray diagram for the...

Sketch a ray diagram for the tip of the chopstick to show why the chopstick looks bent when dipped into water.