Topic 5a- The eye

Question 1

What are the receptor cells in the eye called?

Answer 1

Rods and cones.

Question 2

What is the function of the cornea?

Answer 2

Transparent outer layer found at the front of the eye. It refracts / bends light into the eye.

Question 2

What is the function of the pupil?

Answer 2

It’s the hole at the centre of the eye, through which light enters.

Question 2

What is the function of the sclera?

Answer 2

The tough suppporting wall of the eye

Question 3

What is the function of the iris?

Answer 3

control the diameter of the pupil and therefore how much light enters the eye

Question 4

What is the function of the retina?

Answer 4

The retina contains two types of light receptor cells- one type is sensetive to light intensity and the other is sensetive to colour.

Question 5

What is the function of the lens?

Answer 5

To focus light into the retina

Question 6

What is the function of the optic nerve?

Answer 6

to carry impulses from the receptors on the retina to the brain

Question 6

What are the functions of the ciliary muscles and the suspensory ligaments?

Answer 6

to control the shape of the lens

Question 7

What is the iris reflex and why does it occur?

Answer 7

The iris reflex is when the pupil changes size depending on the light intensity- in very bright light, the eyes dilate so that less light can enter through the pupil and therefore the retina is not damaged by the bright light

Question 8

Describe what happens when the eye is exposed to lots of light?

Answer 8

• circular muscles contract
• radial muscles relax
• therefore the pupil becomes smaller and less light is allowed into the eye

Question 9

Describe what happens to the eye when it is exposed to dim light?

Answer 9

• radial muscles contract
• circular muscles contract
• therefore the pupil becomes wider and more light is able to reach the retina

Question 10

Describe what happens in the eye when it needs to focus on near objects

Answer 10

1. ciliary muscles contract which slackens the suspensory ligaments
2. the lens becomes more curved (fat)
3. this increases the amount by which it refracts light

Question 11

Describe what happens in the eye when it needs to focus on far objects

Answer 11

1. ciliary muscles relax, allowing the suspensory ligaments to pull tight
2. this makes the lense thinner (less curved)
3. this causes the lense to refract light by a smaller amount

Question 12

What is long-sightedness? Why is it caused?

Answer 12

When people are unable to focus on near objects. This is beacuse their eyeball is too short or their lens is the wrong shape meaning the images of near objects are brought into focus behind the retina.

Question 13

What sort of lens should someone with long-sightedness use and why?

Answer 13

A convex lens as it would refract the rays in more causing the image to focus in on the retina

Question 14

What is short-sightedness? What is it caused by?

Answer 14

When someone is unable to focus on distant objects. Caused by the lens in the eye being the wrong shape or the eyeball being too long. This means that images of distant objects are brought to focus in front of the retina