To know how light rays can be
reflected and refracted.
CLUE…
What does this say?
!
Why might it be written
backwards?
To know how light rays can be reflected and
refracted.
Success criteria✓State the law of reflection.
✓Describe how an image is formed by a mirror
using a ray diagram.
✓Show (using a ray diagram) how light is
refracted as it enters and leaves a glass
block.
✓Explain why a pool of water appears to be
shallower than it really is.
TEAM WORKERS
To know how light rays can be reflected and
refracted.
normal
Angle of incidence
DEMO
To know how light rays can be reflected and refracted.
R
eflection i
nvestigation
1. Fix a plane mirror to a piece of paper and draw around it.
2. Draw a normal (at 90°) through the centre of the mirror outline.
3. Use a ray box to shine an incident ray at the mirror – plot the incident and reflected rays.
4. Measure the angles of incidence [i] and reflection [r] and record the results. !
5. Repeat for another four angles of incidence. !
6. What do the results show?
angle i
angle r
Angle of
Angle of
incidence [i] reflection [r]
To know how light rays can be reflected and
refracted.
Write a sentence explaining the relationship
between the angle of incidence and the angle of
reflection.
Angle of incidence
Light box
A
B
mirror
Angle of reflection
To know how light rays can be reflected.
Shiny smooth surfaces reflect
regularly, other surfaces also reflect
light but if the surface is rough the
light is reflected in all directions. We
call this diffuse reflection.
To know how light rays are
refracted.
The answers to these questions are either
a vacuum, water, or air. Choose an answer
for each one.
!
1. Light travels fastest through this
medium.
2. Light travels slowest through this
medium
3. Space is an example of this
4. Light rays are absorbed and reemitted in these 2 mediums
5. The speed of light is approximately
298.9 meters per second through this.
To know how light rays can be reflected and refracted.
Set up your light box and your prism. On your
whiteboards, draw on the path of the light.
To know how light rays can be reflected and refracted.
Why is light refracted?
The speed of light depends on the material through which the light is travelling.
When light enters a different material (e.g. from air into glass), the speed of light changes.
This causes the light to bend or refract.
air
glass
The speed of light is affected by the density of the material through which it is travelling. When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs.
Effects of refraction – the Archer fish
The Archer fish is a predator that shoots jets of water at insects near the surface of the water, e.g. on a leaf. The Archer fish allows for the refraction of light at the surface of the water when aiming at its prey.
The fish does not aim at the refracted image it sees but at a location where it knows the prey to be. image of prey
prey location
To know how light rays can be
reflected and refracted.
To know how light
rays can be reflected and
Refraction
refracted.
PAIRED TALKING
What has happened in each example and why?
I think this is called...
It happens when...
It happens because...
The air is...
The water is...
The light usually travels...but
when it hits water...
To know how light rays can be reflected and
refracted.
Success criteria✓State the law of reflection.
✓Describe how an image is formed by a mirror
using a ray diagram.
✓Show (using a ray diagram) how light is
refracted as it enters and leaves a glass
block.
✓Explain why a pool of water appears to be
shallower than it really is.
TEAM WORKERS
To know how light rays can be reflected and
refracted.
• Explain why a pool of
water appears to be
shallower than it
really is.
4 MARKS
Success criteria-