The Eye

Question 1

What is the eye?

Answer 1

A sensory receptor that detects light and sends electrical impulses along sensory neurones to the brain.

Question 2

How does the eye function?

Answer 2

• light enters through pupil.
• cornea and lens focus light to form a sharp image on the retina.
• retina contains special receptor cells called rods and cones that detect light and form and image.
• the nerves in the retina convert the image into electrical signals that are sent to the brain along the optic nerve.

Question 3

How does the lens change shape to produce a sharp image on the retina?

Answer 3

Object:
Near = ciliary muscles contract = suspensory ligaments are slack = shape of lens is flat and rounded.

Object:
Far = ciliary muscles relaxed = suspensory ligaments are tight = shape of lens is thin and flattened.

Question 4

What do rods do?

Answer 4

They are sensitive to low light intensity and respond only to how dark or light something is.

Question 5

What do cones do?

Answer 5

They are sensitive to bright light and respond to different colours.

Question 6

What is cataracts and how can it be fixed?

Answer 6

It occurs when the lens becomes cloudy so light cannot pass through it properly. The person receives a blurred image on the retina.

Treatment=
replacing the cloudy lens with an artificial lens.

Question 7

When does colour blindness occur?

Answer 7

When at least one type of cone is missing or does not work properly. It is inherited mostly in males.

Question 8

What is long-sightedness and how can it be fixed?

Answer 8

People can focus on distant objects but not on near ones. Eyes are too short.

• corrected with a converging lens because it brings rays together so light is focused on the retina.

Question 9

What is short-sightedness and how is it fixed?

Answer 9

People can focus on near objects but not distant ones. Eyes are too long.

• corrected with a diverging lens to make the rays come together further away.