1. Colour Theory of Light Grade 10 Optics
Write down anything that looks like this!

2. Additive Colour Theory of Light
White light is composed of different colours (wavelengths) of light
The three primary colours of light are:
Red
Green
Blue

3. Additive Colour Theory of Light
If you mix the 3 primary colours, you get white light
The secondary colours produced are:
Red/blue = magenta
Blue/green = cyan
Green/red = yellow

4. Draw these circles & write in colours

5. Investigating Additive Colouring
Draw this table
Filter Combinations
Predicted Colour
Colour Observed
Red & Blue
Red & Green
Blue & Green
Red, Blue & Green
Using a ray box, filters & white paper, observe what colour is produced when you add different filters to the light
Colour options: red, blue, green, magenta, yellow, cyan, white, black

6. Subtractive Colour Theory of Light
Coloured matter absorbs different colours or wavelengths of light
The absorbed colours are subtracted from the reflected light
A black object absorbs all colours
A white object reflects all colours

7. Subtractive Colour Theory of Light
In subtractive colour, primary colours are opposite
Primary colours:
Cyan
Yellow
Magenta

8. Draw these circles & write in colours

9. Subtractive Colour Theory of Light
When you see light, you only see what is reflected
Any colours absorbed will not make it to your eye

10. Investigating Subtractive Colouring
Draw this table
Colour on Screen
Filter Colour
Yellow
Cyan
Magenta
Red
Green
Blue
Fill in the table as we go through the next slides Colour options: red, blue, green, magenta, yellow, cyan, white, black

14. Now some optical Illusions!

15. Negative After-image
Stare, unfocused, at the red cross for 10 seconds then look at the next slide

17. Negative After-image
Cyan

18. Negative Afterimages Your eye has 3 types of colour detecting cells:
Red, green and blue cone cells
Negative afterimages are caused when the eye's cone cells adapt from the over stimulation and lose sensitivity.

19. Negative Afterimages
So staring at red over-stimulates the red cone cell and become less sensitive to red
So you see its opposite colour CYAN, which contains no red!!!
This is true for all of the colours!!

20. Negative After-image
Stare, unfocused, at the flag for 10 seconds then look at the next slide

22. Negative After-image
Cyan
Magenta
Yellow

23. Colour-blindness
Colour-blindness is the inability to distinguish between different colours, caused by a deficiency in the cones of the eye
Red-green colour blindness is the most common and is an inability to distinguish between red and green
Total colour-blindness is very rare!

24. Colour-blindness Test
Normal vision sees 25 and 29
Coloured sees 25 and spots.
Normal-visioned and colourblind people will see different numbers in this test!

25. Another Illusion!
Colour and shapes appear for circles to be moving