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How photoreceptors work

Photoreceptors contain chemicals that change when they are hit by light. This causes an electrical signal, which is then sent to the brain along the optic nerve. Different types of photoreceptor allow us to see an enormous range of light: from starlight to full sunshine, and all the colours of the rainbow.

Photoreceptors in the eye.
Photoreceptors in the eye.
David Becker/Wellcome Photo Library

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