1. Colour Explain why an object appears to be a certain colour.
Explain how a filter changes the colour of light seen.
Describe two ways different colours can be made.

2. Colour
White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.

3. The colours of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Get a worksheet from the front of the class and colour the spectrum.

4. Why are things coloured?
Why is a leaf green, milk white, or a tomato red? When white light hits a leaf most of the colours in the white light are absorbed. Only the green light is reflected. This is the colour that reaches our eye. So we see the leaf as a green colour.

5. Only red light is reflected
Seeing colour
The colour an object appears depends on the colours of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

6. A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light

7. Coloured Filters
Filters such as coloured glass can also change the colour of the light we see. When white light hits a red glass filter, the glass allows the red light to pass through and absorbs the other colours. The colour of the filter tell you what colours it transmits.

8. Using coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a football kit:
Shirt looks red
White
light
Shorts look blue

9. In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Shirt looks black
Blue
light
Shorts look blue

10. Using filters Red Filter
Filters can be used to “block” out different colours of light:
Red Filter
Magenta Filter

11. Experiment: Colours Page 138/139 Science World 9
Work through part A and part B of the experiment using the coloured filters.
Record your observations on a table as shown below.
Answer the questions and conclusion questions.

12. Adding colours
White light can be split up to make separate colours. These colours can be added together again.
The primary colours of light are red, blue and green:
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan
Adding red and green makes yellow
Adding all three makes white again

13. Next Lesson:
Structure of the eye and how colour is seen.