The Eye

Question 1

What is the eye?

Answer 1

A sense organ

That contains receptors sensitive to light intensity and colour

Question 2

What is the cornea?

Answer 2

A transparent lens at the front of the eye

that refracts (bends) light as it enters the eye

(Starts the focusing of the light rays)

Question 3

What is the iris?

Answer 3

The pigmented part of the eye

which controls how much light enters the eye by changing the size of the pupil

Question 4

What is the pupil?

Answer 4

The hole in the iris that allows light to enter the eye

Question 5

What is the lens?

Answer 5

The transparent disc that can change shape to focus light onto the retina at the back of the eye

Question 6

What is the retina?

Answer 6

It contains light receptor cells

Rods - detect light intensity

Cones - detect colour

Question 7

What does the optic nerve do?

Answer 7

It is a sensory neurone that carries impulses between the eye and the brain

Question 8

What is the structure order of how the eye sees light?

6

Answer 8

Cornea
Iris
Pupil
Lens
Retina 
Optic nerve

Question 9

What is the sclera?

Answer 9

The white tough outer layer which protects the eye

Question 10

What is the ciliary muscles?

Answer 10

It can change the thickness and curvature of the lens to allow the eye to focus

Question 11

What is the suspensory ligament?

Answer 11

Fibres that attach the lens to the ciliary muscles

Question 12

What type of focus in the cornea?

Answer 12

A fixed focus

Question 13

What is accommodation?

Answer 13

This is where the lens changes shape to focus on near or distant objects

Question 14

How does accommodation take place?

Answer 14

The lens is surrounded by ciliary muscles which are attached by suspensory ligaments

By contracting/relaxing the ciliary muscles can change the thickness of the lens

When the ciliary muscles contract the suspensory ligament loosens making the lens thicker + refracts light rays more strongly

When the ciliary muscles relax the suspensory ligaments are pulled tight making the lens thinner + only slightly refracts light rays

Question 15

How does accommodation enable us to do us on distant objects?

Answer 15

Distant objects only need to be focused a relatively small amount

So the ciliary muscles relax the suspensory ligaments are pulled tight making the lens thinner + only slightly refracts light rays

The light rays are focused to a point on the retina

Question 16

How does accommodation enable us to do us on near objects?

Answer 16

Light from objects need to be focused on a large amount

When the ciliary muscles contract the suspensory ligament loosens making the lens thicker + refracts light rays more strongly

The light rays are focused to a point on the retina

Question 17

What is long sightedness also called?

Answer 17

Hyperopia

Question 18

What is long sightedness?

Answer 18

People who can focus on distant objects fine

But cannot focus on nearby objects

Question 19

What usually causes someone to be long sighted?

2

Answer 19

Their eyeball being too short which causes light to be focused on a point behind the retina

The lens becomes less elastic which stops the lens becoming thick enough to focus on nearby objects (more common in elderly)

Question 20

How can long sightedness be treated?

Answer 20

By using glasses with convex lenses which partially focus the light before it enters the eye

Question 21

What is short sightedness also known as?

Answer 21

Myopia

Question 22

What is short sightedness?

Answer 22

People who can focus on nearby objects fine

But cannot focus on distant objects

Question 23

What usually causes someone to be short sighted?

2

Answer 23

Their eyeball being too long which causes light to be focused on a point in front of the retina

Can also be caused by the lens being too thick causing the light to be focused in front of the retina

Question 24

How can short sightedness be treated?

Answer 24

Using glasses with concave lenses to partially unfocus the light before it enters the eye