Minimum amount of light for low vision, Physics

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Minimum amount of light for low vision

If 90 photons enter the eye ,10 or less are actually absorbed in photoreceptors.
About 3% are reflected at the surface of the cornea, and about 50% are absorbed in the various structures(cornea, lens, and humors).
Of these that reach the region of the rods ,only about 20% (~10%of the original no.) are absorbed in the rods.
The photons that miss the rods are absorbed in the “backstop”.

Note: Some animals ,such as cuts have a reflective coating behind the rods that give the rods another opportunity to absorb the photons ,these animals have eyes that “glowing in the dark” if a light shines in them.

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