Colour Theory of Light Grade 10 Optics Write down anything that looks like this!
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
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
Draw these circles & write in colours
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
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
Subtractive Colour Theory of Light In subtractive colour, primary colours are opposite Primary colours: Cyan Yellow Magenta
Draw these circles & write in colours
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
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
Now some optical Illusions!
Negative After-image Stare, unfocused, at the red cross for 10 seconds then look at the next slide
Negative After-image Cyan
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.
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!!
Negative After-image Stare, unfocused, at the flag for 10 seconds then look at the next slide
Negative After-image Cyan Magenta Yellow
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!
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!
Another Illusion! Colour and shapes appear for circles to be moving