Light – lesson 3

Target

To know the effect of refraction of light and be able to explain why it happens

Describe what you see when this pencil is placed in the water.

Experiment

Follow these instructions and look at refraction of light using the ray boxes

1. PUT THE GLASS BLOCK ON PAPER – MARK ITS POSTION WITH PENCIL

2. MARK THE RAY OF LIGHT AS IT GOES INTO AND OUT OF THE BLOCK

3. JOIN UP THE POINTS TO SHOW THE PATH OF THE RAY THROUGH THE BLOCK

Experiment 11) Ray gets refracted

3) Ray still gets refracted but not deflected

2) Ray still gets refracted

Experiment 2 Now draw the diagrams shown in your book

Rays of light going in a glass block

Explaining refraction

Imagine a car driving from the road into a muddy field.

In the muddy field it slows down as there is more friction.

If it enters the field at an angle of incidence of other than 0 then the front tyres hit the mud at different times.

Tyre one hits the mud first and will move more slowly than tyre two.This causes the car to turn towards the normal.

When the car leaves the mud for the road, tyre one hits the road before tyre two and this causes the car to turn away from the normal.

Mud

Road

Tyre 1 Tyre2

RefractionRefraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that light waves will travel through. When a ruler is placed in water it looks like this:

In this case the light rays are slowed down by the water and are _____, causing the ruler to look odd. The two mediums in this example are ______ and _______.

Words –

speed up, water, air, bent,

medium