12.5 Spectrum of white light and coloured light

12.5 Spectrum of white light and coloured light

Sometimes, if it rains and the Sun shines at the same time, you may see a rainbow. You have to stand with your back to the sun; you will see an arch of beautiful colours looking as though is is hanging on the air

Multiple Choice

How many colours are in the rainbow?

• 7

• 5

• 6

• 8

Splitting light

• You can see the colours of the rainbow for your self by sending a ray of white light into a glass of prism.

• A prism is a triangular glass box

• When the light enters the prism it bends-it is refracted. It also bends as it leaves the prism.

Splitting light

• The white light split up into a spectrum of colours. Same colours as you see in the rainbow.

• The splitting up of white light into separate colours is called dispersion

Multiple Choice

Which colour is refracted most as it passes through the prism?

• red

• orange

• violet

• blue

Multiple Choice

Which colour is refracted least as it passes through the prism?

• red

• orange

• violet

• blue

Multiple Choice

What is the transparent material that causes this?

• spectrum

• splitting light

• water(raindrop)

Open Ended

To remember the colours in the spectrum, some people write this: Roy G. Biv. It looks like a name. How will this help them remember the order of the colours?

Dispersion

This happens because of refraction. When white light enters a block of glass, some colours bend more than the others. Violet bends the most, red the least.

Multiple Choice

Which colour of light is refracted more by prism?

• green

• blue

12.6 Coloured light

• A filter is a piece of coloured plastic or glass. It only gets through some of the colours which make up white light. It absorbs the other colour.

Multiple Choice

Which colours can pass through a blue filter?

• yellow

• red

• blue

• green

Multiple Choice

Imagine that you put a green filternext to a blue filter, so that white light had to pass through one filter after the other. WOuld any light come through?

• Yes, some green and blue would pass through,

• No colours would pass through

Multiple Choice

Which two filters, if placed together, would absorb all colours of light?

• Red and green

• red and blue

• All of the above

Open Ended

Which colour of light are reflected by a black object?