Refraction Of Light 01/10/2024

What is happening
in each of these
photos?
 Learning Objectives

(L4) Can describe

(L3) Can state how light bends (L5) Explain why
what happens to towards or away
refraction
light as it hits from the normal
glass at an angle. when it changes happens.
medium.

Key Words: refraction, normal, incidence, normal,

emergence
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

http://www.bbc.co.uk/learningzone/clips/refraction/13525.html

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/refraction/index.html
1 Draw a line around the glass block;

2 Draw a normal line, on one side of the glass, which is at a

right angle to the surface of the block;

3 Use a ray box to shine a ray of light into the glass block,
entering it at the normal line;

4 Mark the path of the ray of light through the block with
two crosses;

5 Mark the position of the light leaving the glass block with
two crosses,

6 Remove the glass block and draw a normal line at the

point where the light exits;

7 Plot the path of the ray of light.

 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

Investigating refraction Angle of Angle of Angle of

incidence refraction emergence
i r e
e 
glass block
r 


i
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

In pairs you
need to
collect

Everything
shown in this
diagram plus a
protractor!
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

I noticed that the ray of light is refracted (away

from/towards) the normal when it goes into a glass block.

The ray of light is refracted (away from/towards) the

normal when it comes out of a glass block.

The angle of incidence is (smaller than/equal to/larger

than) the angle of emergence.

The angle of refraction is (smaller than/equal to/larger

than) the angle of incidence.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

Why was the light refracted?

WHY did the light bend both as it went
into the glass block and as it left the
glass block?

Talk to the person next to you about this

for 1 minute.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

The light ray bends away

from the normal again when
it travels into air which is
less dense.

This is because glass is

more dense than the air
and it slows down the
The light ray bends towards
light.
the normal when it enters the
glass from the air.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

Can you now explain

what is happening in
each of these photos?
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

This diagram shows what

happens to light which is
reflected by the pencil.

The light bends when it

leaves the water.

Your brain thinks that

light always travels in
straight lines so the pencil
tip seems to be nearer the
surface than it really is.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

• Because of this
bending, a fish in
water looks nearer to
the surface than it
really is.

• Aborigine hunters
have trained
themselves to correct
for this when fishing
so that they catch
their tea successfully.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

1 The disappearing coin

trick works by refraction.

a) Copy the two lower

diagrams and complete
the second one.

b) Explain how the trick

works.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

1. The disappearing coin trick

works by refraction.

b) Explain how the trick

works.

The water
refracts the
light rays
coming from
the coin.
 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

When a pencil is put into a beaker

of water it looks ______. This is
because the light is __________
as it leaves the water. The light
travels _________ in air than
water

Choose three of these words to complete the sentences

slower reflected bent faster refracted

 (L4) Can describe how
(L3) Can state what (L5) Explain
light bends towards or
happens to light as it why refraction
away from the normal
hits glass at an angle. happens.
when it changes medium.

When a pencil is put into a

beaker of water it looks bent.
This is because the light is
refracted as it leaves the water.
The light travels faster in air
than water

Choose three of these words to complete the sentences

slower bent
 What is Refraction?
• Refraction is the bending of
light as it passes from one incident ray
transparent material into
another. air
glass

• This is what causes refracted

ray
distortion when you look at
an object placed
underwater, or when you
hold a pair of spectacles emergent ray
away from your face and
look through it.
 What Causes Refraction?
• Refraction depends on the speed of light in
the substance.
• Light bends towards the normal when it slows
down as it crosses to the other medium.
i angle of incidence

Air

Glass
angle of refraction
r
Refractive Index = Sini/sinr
Speed of Light in Some Substances

Medium Speed of light

(×108 m s-1)
Diamond 1.25 Means the numbers given
are multiplied by 108
Glass 2.00 metres per second.

Perspex 2.00 In air, the speed of light is

300 000 000 m/s!
Water 2.25

Ice 2.30

Air 3.00
 Using Ray Diagrams
Refractive Index
• Object placed
underwater.
• Object appears to
be more shallow
than it actually is.
light bends away from normal because it
Air
speeds up as it travels from glass into air
Water
Apparent
depth Real
Light rays appear to
depth
come from here.

Actual object
Method for Drawing Ray Diagrams
• Object partially in water appears bent.
◼ Light from the end of the rod appears to be
coming from a higher location than it actually is.

Air
Water Apparent
position

Real
position
 Test Your Understanding
• A ray of light is vertically incident on a
horizontal glass surface.
• Does the ray refract?
light ray

air

glass
 Effects and Uses of Refraction
• Effects:
– Objects under water or under a piece of glass
appear shallower than they actually are.
– When looking upwards from underwater, objects
above look higher than they actually are.

• Uses:
– Lenses: magnifying glasses, spectacles, etc.
– Prisms: Dispersion of light into colours
 Differences b/w Reflection and
Refraction
• 3 main differences:
Reflection Refraction
No change in speed of light before Speed of light before and after
and after reflection refraction is different

Angle of incidence = angle of Angle of incidence ≠ angle of

reflection refraction

Light ray does not pass from one Light passes from one medium
medium into another into another
Quiz!
1 Refraction is what happens when light:

A hits an opaque object.

B bounces off a mirror.
C is scattered by a rough surface.
D bends as it goes from one substance
into another.
2 Refraction occurs because

A light speeds up when it meets a denser

transparent material.
B light slows down when it meets a denser
transparent material.
C light stops when it meets a denser
transparent material.
D light reflects inside denser transparent
materials.
3 Which diagram shows the correct rays?

A B C D
4 Where does refraction take place?

A in the centre of a transparent substance

B all the way through a transparent
substance
C as light travels from one opaque
substance into another
D as light travels from one transparent
substance into another
1 Refraction is what happens when light:

A hits an opaque object.

B bounces off a mirror.
C is scattered by a rough surface.
D bends as it goes from one substance
into another.
2 Refraction occurs because:

A light speeds up when it meets a denser

transparent material.
B light slows down when it meets a
denser transparent material.
C light stops when it meets a denser
transparent material.
D light reflects inside denser
transparent materials.
3 Which diagram shows the correct rays?

A B C D
4 Where does refraction take place?

A in the centre of a transparent substance

B all the way through a transparent

substance
C as light travels from one opaque
substance into another
D as light travels from one transparent
substance into another
 Learning Objectives
Are you now able to…

(L4) Can describe

(L3) Can state how light bends (L5) Explain why
what happens to towards or away
refraction
light as it hits from the normal
glass at an angle. when it changes happens.
medium.
:( :| :)

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.