Which part of the eye contains millions of light-sensitive cells that detect light?

• A. Cornea
• B. Sclera
• C. Iris
• D. Retina

Answer: (D)

Light detection occurs in the retina, a layer of light-sensitive tissue lining the back of the eye. It houses millions of photoreceptor cells—rods and cones. Rods are highly sensitive in dim light and help with movement awareness, while cones detect color and fine detail. When light hits these cells, it’s converted into electrical signals that travel through the optic nerve to the brain for interpretation.

The cornea is the transparent front surface that helps focus light but does not contain photoreceptors. The sclera is the protective white outer layer. The iris controls how much light enters by changing the pupil size, but it does not detect light either.