SB2h The Eye

Question 1

Retina?

Answer 1

.Located at the back of the eye
.Contains receptor cells that detect light

Question 2

Pupil?

Answer 2

.Dark (black) area in the middle of your eye where light enters​
.The amount of light entering is controlled by muscles

Question 3

Iris?

Answer 3

.Coloured part of your eye that surrounds the pupil
.Contains muscles which constrict the pupil (decrease its diameter, letting less light in) or dilate it (make it bigger, to allow more light in)​
.Helps protect the eye as bright light can damage the retina

Question 4

Cornea?

Answer 4

.Light entering the eye needs to be focused onto a point in the retina to produce a clear image.
.Most focusing is done by the cornea, which bends (refracts) light rays, bringing them together

Question 5

Lens?

Answer 5

.Involved in focusing
.Fine tunes the focusing to ensure the image on the retina is sharp and clear

Question 6

Ciliary muscles?

Answer 6

.Make the lens fatter to focus on light from near objects (more refraction) or thinner to focus on light from distant objects (less refraction)

Question 7

Cone cells? 4

Answer 7

.Receptor cells that are sensitive to colours of light
.Some cones detect red light whereas others detect green or blue
.Generate impulses in sensory neurones which lead to the brain via the optic nerve
.Information from the cones is processed into full colour vision at the back of the cerebral hemispheres

Question 8

Rod cells? 3

Answer 8

.Receptor cells that detect different light intensities (not colour)
.Rods work well in dim light whereas cones only work in bright light​
.This is why we have poor colour vision in dim light

Question 9

Cataracts?

Answer 9

caused by protein build up inside the lens, making it cloudy.

Question 10

Colour-blindness?

Answer 10

.Caused by cone cells not working properly, so people have difficulty seeing some colours

.Most common from is red-green colour blindness, where the cones that detect green light are faulty
.These people cannot tell the difference between reds, greens and browns

.There is no cure for colour blindness

Question 11

Long-sightedness? (3)

Answer 11

.caused by eyeball being too short or the cornea not being curved enough
.close objects appear blurred
.light focuses behind retina

Question 12

Short-sightedness? (3)

Answer 12

.caused by the eyeball being too long or the cornea being too curved bending light rays more than it should
.distant appear blurred
.light from object focuses in front of retina

Question 13

Treatments for long-sightedness?

Answer 13

.glasses with converging lens to bend the rays before they reach the eye
.laser eye surgery which cuts away some of the cornea to reshape it

Question 14

Treatments for short-sightedness?

Answer 14

.glasses with diverging lens to spread out the rays before they reach the eye
.laser eye surgery which cuts away some of the cornea to reshape it

Question 15

Treatment for cataract?

Answer 15

full colour vision can be restored by replacing the clouded lens with a plastic one.