What are the photosensitive cells that enable night vision, and where are they found in the human eye?
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A
Cones are responsible for night vision and are located primarily in the peripheral retina.
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B
Rods are responsible for night vision and are concentrated in the central retina.
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C
Rods are responsible for night vision and are located primarily in the peripheral retina.
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D
Cones and rods are equally sensitive to light, and both are concentrated in the fovea.
Refer to figure.
HUMAN EYE
The human eye consists of three layers:
i) outer layer (sclera and cornea)
ii) middle layer (uvea)
iii) inner layer (retina)
INNER LAYER
The retina is a light-sensitive layer inside the eyeball where the photoreceptors are found. Images are focused on the retina where the photoreceptors convert them into nerve impulses that are then transferred the brain. The retina has two types of photoreceptors:
1. Rods: They are found in the periphery of retina and they enable scotopic (low-light) vision. The rods can only create black and white images and are also responsible for peripheral vision.
2. Cones: The fovea, at the retina's center, contains only cones that enable photopic (bright-light) vision. The cones are responsible for direct vision and require bright light to function. They are used to detect colours.
Rods → Night vision, Peripheral vision (black and white images)
Cones → Day vision, Central vision (colourful images)
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