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  • em1461
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em1461 created the topic: Cpl

The fact that the concentration of cones is greatest at the fovea while the rods are distributed over the whole of the retina means that:

A) night vision is best achieved by lookig directly at the object
B) colour sensitivity is best away from the fovea
C) at night the eye effectively has two blind spot
D) none of the above are correct
#1

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  • DAH
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DAH replied the topic: Cpl

I'd say none are correct.
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baddles replied the topic: Cpl

I think it is C.

At night, the available light is below the threshold which can be seen by the cones. The photoreceptors in the fovea are almost all cones, so the fovea is effectively 'blind'.

It's not A because night vision is improved by looking slightly to one side of the target.
It's not B because colour vision is available only in the fovea.
I think D is a "distractor" to make us uncomfortable about C.
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