Biology / Unit 12 Bio 2907 short lesson, about 20 seconds
Rods versus Cones
Captions available
The idea
Rods are strongly photosensitive photoreceptors at the retina's edges, specialized for dim, achromatic peripheral vision; cones are weakly photosensitive, concentrated at the fovea, specialized for color vision.
In practice
Looking slightly away from a dim star lets rod-dense peripheral retina detect it better than looking straight at it.
Where people slip
Cones, not rods, dominate the fovea — sharpest vision favors color and detail over sensitivity.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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