How do we see colour?

The Spectrum White light is made up of many different colours. The range of colours in white light is called the spectrum. White light can be split into its spectrum by refraction (bending) of the light as it passes through glass or water.

The colours of the spectrum - ROYGBIV Red Orange Yellow Green Blue Indigo Violet

Mixing Colours Light has three primary colours. They are: Red Blue Green (it’s different from paintbox primary colours!) Colours can be mixed to make other colours and white light.

Red Magenta Yellow White Blue Green Cyan

How and why we see colour http://www.amonline.net.au/colour/colour14.swf

How does color work? When light hits an object, it either reflects (bounces off) or is absorbed. An object’s color depends on which colours of light are absorbed and reflected. A red object looks red because it reflects red light. All other colours are absorbed.

Colour questions. Explain why a green leaf looks green. Because it reflects green light. All other colours are absorbed by the leaf. What colour(s) does a white object reflect? A white object reflects ALL of the colours. Explain what happens when light hits a black object. A black object absorbs ALL of the colours. What 2 colours make yellow light? Yellow is made up of red and green light. Explain what colours are absorbed and reflected by a yellow banana. A banana reflects red and green light and absorbs blue light.

Red and green

If all of the light colours reflect then the object looks white.

If all of the light colours are absorbed and no light is reflected, then the object looks black.

Filters and coloured lights Colour filters absorb some light and only allow one colour through. Eg – a red filter only lets red light pass through it. Red filter White light (all colours)

Objects through coloured filters If we look at an object under a coloured light or through a coloured filter, its colour may appear to change.

Coloured Objects - questions What colour would a green box be in red light? Green box in white light A green box in red light would appear black because it absorbs the red light and there is no green light available to reflect. ? What colour would it be in red light…?

Copy the following table showing what colour each object would look in different colours of light: Colour of object White light Red light Blue light Green light Yellow light Cyan light Magenta light white black red blue green yellow cyan magenta

When a ray of light passes through a prism, it is refracted (bent) then dispersed (spread out) into the different colours of the spectrum. The colours bend at different angles because their wavelengths are different. Purple light bends the most and red light bends the least.

Since red’s wavelengths are longer, they bend the least when passing through the prism Violet’s are shortest, so they bend the most.