Unit 6
6.1 Reflections 6.2 Refraction
6.3 Making rainbows 6.4 Colors of light
6.5 Galaxies 6.6 Rocks in space
2nd Semester
Unit 6: Light
6.2 Refraction
Coursebook: Page 192
Learning Objectives
8Ps.02 Describe refraction of light at the boundary between air and glass or air
and water in terms of change of speed.
By the end of this lesson you should be able to:
❏ Predict which direction (toward or away from the normal) light will bend when
passing between air and either glass or water, or going the opposite way
❏ State whether light will speed up or slow down when crossing a boundary.
❏ Construct ray diagrams for refraction at air-glass and air-water boundaries and
the opposite way.
For this lesson you will need:
New Terms
Distorted Refraction Medium
Away from the
Bent Towards the normal
normal
Angle of incidence Angle of refraction Lenses
Quizlet Set
Why do you think you can’t see clearly when you
look through a glass of water?
The image is distorted (less clear)
Refraction
But why?
Is this pencil really bent?
If not, why does it look that
way?
The change in direction of light on
passing from one medium to another
because of change in speed
225 000 km/s 200 000 km/s 125 000 km/s
Medium?
Another material
with a different
density
It slows down as it goes through different
mediums
Change in speed = Change in direction
Light passing from air into water or glass
First light slows down when it enters
water or glass
This causes it to change direction.
The light is bent towards the normal.
The angle of incidence is greater than
the angle of refraction.
Light passing from glass or water into air
What will happen to the speed of light?
Will is speed up or slow down?
Will it bend towards or away from the
normal?
Light speeds up when it enters the air
from the glass or water
This causes it to change direction.
The light is bent away from the normal
The angle of incidence is smaller than
the angle of refraction.
Refraction in everyday life
Refraction in everyday life
Question 1
Complete the sentences, using ‘faster’ or slower.
a Light travels … in water than it does in air.
b Light travels … in air than it does in glass
Question 2
Complete the sentence to describe refraction correctly.
Refraction of light happens when light … direction because of a
change in ….
Practice!
Question 3
This ray diagram shows a ray of light in air.
Copy and complete the ray diagram to show what happens when the
ray of light enters the glass.
Include on your diagram:
• the normal
• the angle of incidence
• the refracted ray
• the angle of refraction.
Practice!
Question 4
This ray diagram shows a ray of light in water
Copy and complete the ray diagram to show what happens when the
ray of light enters the glass.
Include on your diagram:
• the normal
• the angle of incidence
• the refracted ray
• the angle of refraction.
Practice!
Check your
understanding
Success Criteria
❏ I can predict which direction (toward or away from the normal)
light will bend when passing between air and either glass or
water, or going the opposite way
❏ I can state whether light will speed up or slow down when
crossing a boundary.
❏ I can construct ray diagrams for refraction at air-glass and air-
water boundaries and the opposite way.
