OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Which part of the eye is responsible for detecting light?

1. The lens

2. The retina

3. The cornea

4. The iris

The correct answer is: The retina

The retina is the part of the eye responsible for detecting light. It is a thin layer of tissue located at the back of the eye, containing millions of photoreceptor cells called rods and cones. Rods are sensitive to low light levels and are primarily responsible for night vision, while cones function in brighter light and enable color vision. When light enters the eye, it is focused by the cornea and the lens onto the retina, where the photoreceptors convert the light into electrical signals that are sent to the brain via the optic nerve. This process allows us to see and interpret our environment. In contrast, the lens helps to focus light onto the retina but does not detect light itself. The cornea also plays a role in bending light to assist with focus but does not contain the light-detecting cells needed for vision. The iris controls the size of the pupil, regulating the amount of light that enters the eye, but it does not partake in the detection of light. Therefore, the retina's role as the light-detecting structure is essential for vision.