REFRACTION

When a car drives through a puddle, it will slow down becauseOf drag on the wheels caused by the water

If the puddle is at right angles to the car, it will continue to travel straight

REFRACTIONIf the puddle is at an angle, as shown here, one wheel will slow down first, causing the car to turn.When the other wheel hits the water, it too will slow.The wheels will leave the puddle at different times causing one to speed up first, and the car will straighten up

If the puddle is at right angles to the car, it will continue to travel straight

REFRACTION

The greater the angle , the more time before both wheels are in the waterSo the greater the angle of bending

The deeper the water, the more the first wheel will slow downSo the greater the angle of bending

Refraction

The waves of light will behave the same way

The more optically dense the medium, the greater the bending of the light

Refraction

Refraction is caused by light changing speed

The ratio of speed of light in a vacuum to the speed of light in a medium is known as the refractive index

= Every transparent substance will

have its own refractive index

Refraction

Substance Refractive index

water 1.33

alcohol 1.36

oil 1.45

plastic 1.50

glass 1.52

diamond 2.41

Refraction

= 1.50

1. The speed of light in a vacuum is 3.0 x 108 ms -1 and in chloroform its speed is 2.0 x 108 ms -1 . Calculate the refractive index value, n, for chloroform.

=

Refraction

In which transparent substance does light travel the slowest?

• The higher the refractive index, the slower light travels - diamond

In which 'substance' does light travel the fastest?

• The lower the refractive index, the faster light travels - water

Refraction

Calculate the speed of light in glass

= 1.50

So =

= 2.0 x 108 ms-1

Refraction

Calculate the speed of light in water

= 1.33

So =

= 2.26 x 108 ms-1

Refraction

Calculate the speed of light in diamond

= 2.41

So =

= 1.24 x 108 ms-1