Why do objects have no color in dim light?

Answer: Rod cells don't detect color

Rod cells don't detect color ✓ — Correct! The retina has two photoreceptor types: cones (detect color, need more light) and rods (detect brightness, very sensitive). In dim light, cones don't receive enough photons to activate. Rods dominate—they're monochromatic (detect light intensity only). Result: scotopic vision (night vision)—you see shapes and movement but not colors. 'At night, all cats are gray!'

Brain removes color at night — Wrong. Brain doesn't remove color. Cone cells simply don't activate in dim light—insufficient photons. Rods take over, providing only brightness information.

Pupils block color information — Wrong. Pupils don't block color. Color disappears because cone cells need more light than available, leaving only rods (which don't detect wavelength).