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What is colour?
The
retina of the eye is sensitive to electromagnetic waves over a range of frequencies
that we call light waves. Together these form white light. The eye senses these
waves in two ways. One set of sensors, called rods, will detect any of this
light irrespective of wavelength and the brain records this as lightness or
darkness, rather like the old black and white TV. The other set, called cones,
come in threes, each sensitive to a particular frequency (we call red,
green and blue) and the brain records the amount of light from these, putting
them together to create all manners of colour rather like a colour TV. For example, taking a maximum
reading from a red cone and a half amount of green creates orange. Try
mixing colour yourself.