The eye

Question 1

Describe how light is focused from a near object onto the retina. (4 marks)

Answer 1

-Light rays diverge and need to be refracted by the lens
-Ciliary muscles contract
-Suspensory ligaments loosen
-Lens is more convex
-So more refraction

Question 2

How does a reflex involving the iris protect the retina from bright light? (3 marks)

Answer 2

-Circular muscles contract
-Radial muscles relax
-Pupil constricts
-Less light enters the eye, preventing damage to the retina

Question 3

What is the role of the retina?

Answer 3

Light passes through to here
Contain light receptor cells (rods and cones)

Question 4

What is the difference between rods and cones?

Answer 4

Rods are useful in black and white and in dim light
Cones help us see in colour and bright light

Question 5

What is the role of the optic nerve?

Answer 5

Sends electrical impulses from the retina to the brain.

Question 6

What is the iris?

Answer 6

It is the coloured part of the eye which controls how much light enters the eye.

Question 7

What is the cornea?

Answer 7

Transparent region of the sclera at the front of the eye, it refracts light as it enters the eye.