Located at the back of the eye, this part focuses light onto nerve fibers that connect to the optic nerve to send images to the brain.

• A. Cornea
• B. Retina
• C. Optic nerve
• D. Lens

Answer: (B)

The key idea is identifying the structure at the back of the eye that detects light and provides the signals to the brain. The retina sits at the back of the eye and contains photoreceptors (rods and cones) that detect light. These cells convert light into electrical signals, which travel through a network of retinal neurons that bundle together to form the optic nerve and carry visual information to the brain. The cornea and lens do the front-end focusing of light, but they’re not at the back and don’t send signals to the brain themselves. The optic nerve carries signals away from the eye, not detect light. So the retina best fits the description.