B10.5 The eye

Question 1

What is the retina?

Answer 1

All the light sensitive cells are arranged together inside the back of the eye in a special light sensitive layer known as the retina

Question 2

What is the sclera?

Answer 2

White outer layer of the eye - it is relatively tough and strong so they eyeball is not easy damaged

Question 3

What is the cornea?

Answer 3

Transparent area at the front of the eyeball that lets light into the eye

Question 4

What is the purpose of the curved surface of the cornea?

Answer 4

Changing the direction of the light rays coming into the eye - making sure that as they enter the eye they are focused on the retina

Question 5

What is the pupil?

Answer 5

A hole which lets light enter the eye - controlling the amount of light entering the eye

Question 6

What is the purpose of the iris?

Answer 6

Controls the size of the pupil
It is made up of muscles that contract or relax to change the size of the pupil - to control the amount of light reaching the retina

Question 7

What happens in dim light?

Answer 7

Pupil is enlarged so as much light as possible enter the eye

Question 8

Why is it important to regulate the amount of light that enters the eye?

Answer 8

That too much light cannot damage the delicate light - sensitive cells

Question 9

What is the lens held by?

Answer 9

The suspensory ligaments and ciliary muscles

Question 10

What is the purpose of the lens?

Answer 10

It fine tunes the focusing of the light rays - changing their direction to produce a clear image on the retina

Question 11

Why is the eye a spherical shape?

Answer 11

Filled with a thick transparent jelly

Question 12

What happens in bright light?

Answer 12

Circular muscles contract
Radial muscles relax
Pupil constricts to let less light enter into the eye

Question 13

What happens when the light hits the retina?

Answer 13

Light-sensitive cells are stimulated. Send impulses to the brain along sensory neurones in the optic nerve
Brain receives these messages it interprets them as a visual image

Question 14

What is a blind spot?

Answer 14

The point where the optic never leaves the eye has no retina so there is a blind spot
You are unaware of the blind spot because the brain fills in the gaps

Question 15

What happens if the light is focused in front or behind the retina?

Answer 15

The image will be blurred

Question 16

How does the light get focussed?

Answer 16

By the process of refraction - where light changes direction as it passes through the eye. The cornea and the jelly in the eye change the direction of the light rays onto the retina - always refract the same amount

Question 17

How can the shape of the lens be changed?

Answer 17

By the relaxation of the ciliary muscles
When the ciliary muscle relaxes, its diameter becomes wider; the suspensory ligaments tighten and pull the lens thinner. This happens when focussing on a distant object

Question 18

Why is changing the amount of light the lens refract importantl?

Answer 18

See both close and distant objects in focus

Question 19

What is the problem formed by the image?

Answer 19

It is upside down - brains interpret the image as the right way up