1. Light

2. Passing white light through a prism

3. Richard Of York Gave Battle In Vain
Splitting white light
A prism splits a ray of white light into the colours of the rainbow.
This process is known as dispersion.
The colours that make up white light are called the spectrum.
Dispersion occurs because different colours of light refract differently. Red light refracts the least; violet light the most.
The order of the colours in the spectrum is always the same. Use this phrase to remember the order of colours:
Richard Of York Gave Battle In Vain Y

4. Natural dispersion
If there are water droplets in the air and the sun is illuminating them from behind, then you may see a rainbow in the air.
Light enters the water droplets and refracts. It then reflects off the back of the rain drop.
The red light refracts the least and the violet the most. This causes dispersion of the sunlight.
Photo credit: © 2008 Jupiterimages Corporation

5. The visible light spectrum

6. Recombining colours

7. Mixing coloured light

8. How do we see different colours?

9. Seeing different colours
How do we see the different colours in this frog and lily?
The frog’s red skin absorbs all of the colours except red and so it appears red.
The black skin absorbs all colours. No colours are reflected and so it appears black.
The lily’s centre absorbs all colours except red and green. It reflects red and green light, and so appears yellow.
The leaves reflect all the colours and so appear white.
Photo credit (top): © 2007 Jupiterimages Corporation
Photo credit (bottom): © 2007 Jupiterimages Corporation

10. Using filters of primary colours
A filter absorbs some colours of white light and lets other colours through to create coloured light.
A red filter absorbs all colours…
…apart from red light.
A blue filter absorbs all colours…
…apart from blue light.
A green filter absorbs all colours...
…apart from green light.

11. Using filters of secondary colours
A magenta filter absorbs all colours…
…apart from red and blue.
A cyan filter absorbs all colours…
…apart from green and blue.
A yellow filter absorbs all colours...
…apart from red and green.

12. Seeing colours in coloured light

13. How do we see colours in coloured light?

14. The electromagnetic spectrum

15. Colour summary