Colour vision

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Colour vision is the capacity of an organism to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. Colour is a quality constructed by the visual brain and not a property of objects.

A 'red' apple does not emit red light.[1] Rather, it simply absorbs all the frequencies of visible light shining on it except for a group of frequencies that are reflected.

It is these frequencies which are perceived as red.

Mechanism[change | edit source]

The nervous system derives colour by comparing the responses to light from the several types of cone photoreceptors in the eye. These cone photoreceptors are sensitive to different portions of the visible spectrum.

For humans, the visible spectrum ranges approximately from 380 to 740 nm, and there are normally three types of cones. The visible range and number of cone types differ between species.

The advantage of colour vision is the better discrimination of surfaces it allows.[2]

References[change | edit source]

  1. Wright, W.D. (1967). The rays are not coloured: essays on the science and vision and colour. Bristol: Hilger. ISBN 0-85274-068-9.
  2. Kreft S and Kreft M 2007. Physicochemical and physiological basis of dichromatic color. Naturwissenschaften 94, 935-939. On-line PDF