Colour Vision

Edexcel A-level BiologyMammalian Nervous SystemLesson 28 of 38

Humans can see colour because there are three types of cone, each containing a different form of iodopsin. Each type absorbs light over a range of wavelengths, with its peak at a different point in the spectrum:

• blue-sensitive cones: peak about 420 nm
• green-sensitive cones: peak about 530 nm
• red-sensitive cones: peak about 560 nm

The ranges overlap, so light of most wavelengths stimulates more than one type of cone. This is the trichromatic theory of colour vision: the brain works out the colour of light from the relative amounts by which each type of cone is stimulated.

More in Mammalian Nervous System

• The Human Eye
• The Retina
• Rods
• Cones
• Formation of the Brain
• Major Areas of the Brain
• Other Areas of the Brain
• Spinal Cord

All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics