Why can't we see in complete darkness?

Answer: Eyes detect reflected light only

Eyes detect reflected light only ✓ — Correct! Vision requires light. Eyes detect photons reflected off objects. In complete darkness (no light source), no photons reach your eyes, so photoreceptors (rods and cones) have nothing to detect. Cats see better in dim light (more rods, tapetum lucidum), but nothing sees in absolute darkness!

Brain shuts down night vision — Wrong. Night vision (rod cells) activates in darkness. But without any light photons to reflect off objects, even adapted eyes can't see.

Darkness blocks eye signals — Wrong. Darkness doesn't block signals. Eyes simply have no photons to detect. Vision requires light—eyes are light detectors, not light emitters.