THE EYE

Question 1

how does the eye focus light on the retina?

Answer 1

by changing the shape of the lens- which is known as accommodation

Question 2

describe the reflex for focusing on near objects

Answer 2

1) the ciliary muscles contract causing the sensory ligaments to slacken
2) the lens becomes more curved
3) this increases the amount by which is reflects light

Question 3

describe the reflex for looking at distant objects:

Answer 3

1) the ciliary muscles relax which allows the shape sort ligaments to pull tight
2) this makes the lens thin and less curved
3) so it refracts light by a smaller amount

Question 4

what is the sclera?

Answer 4

tough supporting wall of the eye

Question 5

what is the cornea?

Answer 5

transparent outer layer found at the front of the eye which refracts light into the eye

Question 6

what is the iris?

Answer 6

contains muscles that allow it to control the diameter of the pupil therefore how much light enters the eye

Question 7

what is the lens?

Answer 7

the lens focuses the light onto the retina which contains receptor cells sensitive to light and colour

Question 8

what does the optic nerve do?

Answer 8

carries impulses form the receptors on the retina to the brain

Question 9

what is the shape of the lens controlled by?

Answer 9

the ciliary muscles and the suspensory ligaments.

Question 10

what happens when the light receptors in the eye detect very bright light?

Answer 10

when it detects bright light a reflex is triggered that makes the pupil smaller

the circular muscles in the iris contract and the radial muscles relax which reduces the amount of light that can enter the eye