7 (a) (i) Which part of the eye carries impulses to the brain? A cornea B iris C lens D optic nerve (ii) Name the structure within the eye that controls the amount of light entering the eye - Edexcel - GCSE Biology - Question 7 - 2020 - Paper 1

The structure within the eye that controls the amount of light entering is the iris.

The two types of cells in the retina that detect light are rods and cones.

• Rods are responsible for vision in low-light conditions. They do not detect color but are very sensitive to light, allowing us to see in dim environments.
• Cones, on the other hand, function well in bright light and are responsible for color detection. There are three types of cones sensitive to different wavelengths of light (red, green, and blue), facilitating our ability to perceive a wide range of colors.

The type of drug used to treat infections caused by bacteria is antibiotics.

Short-sightedness (Myopia)

• The eyeball is too long, which causes light rays to focus in front of the retina.
• The cornea may be too curved.
• The lens can be too curved or too convex, leading to excessive refraction of light.

Long-sightedness (Hyperopia)

• The eyeball is too short, causing light rays to focus behind the retina.
• The cornea is not curved enough.
• The lens may be too thin or not convex enough, leading to insufficient refraction of light.