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 | change 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.

With colour vision gets better vision (more information) about the things it sees.[2] This lets it see when fruit or vegetables are ripe, and lets it see animals hiding from plain sight. The advantage of colour vision is mainly in the daytime. At night the main problem is to collect light and see in the weak light. This is something rods do better than cones.

Related pages[change | change source]

References[change | change 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