The Eye

Question 1

Iris function

Answer 1

Controls size and shape of pupil

Question 2

Pupil function

Answer 2

Shape determines the amount of light entering the eye

Question 3

Lend function

Answer 3

Focus light onto retina - adjusts shape to change refractive index

Question 4

Cilliary muscles function

Answer 4

Controls lens size

Question 5

What is accommodation?

Answer 5

When the eye can focus on objects at different distances

Question 6

How does a lens adapt to see a near object?

Answer 6

Tenses - lens thicker - power increases

Question 7

How does a lens adapt to see a far object?

Answer 7

Relaxes - lens thinner - power decreases

Question 8

Choroid function

Answer 8

Supply oxygen to eye (blood vessels)

Question 9

Fovea function

Answer 9

Sharpest image created when light focuses on this area - due to high concentration of cones

Question 10

Retina function

Answer 10

Light sensitive layer of cells that is focuses on by the lens

Question 11

Optic nerve function

Answer 11

Transmits image in the form of electrical signals to brain

Question 12

Blind spot function

Answer 12

No retina at this point due i optical nerve - so no image formed in this area

Question 13

Aqueous humour function

Answer 13

Watery, clear liquid that allows light to reach retina - low refractive index

Question 14

Vitreous humour function

Answer 14

Black liquid keeps eye’s shape

Question 15

Cornea function

Answer 15

Focus light as it has high refractive index

Question 16

What is more common in the eye? rods or cone cells

Answer 16

Rods - 20x more common

Question 17

What cells are used in low levels of light?

Answer 17

Rods

Question 18

What cells are used in high intensity light?

Answer 18

Cones

Question 19

Why are colour images more detailed?

Answer 19

Incorporate more wavelengths to differentiate between

Question 20

Why do rods see in low detail?

Answer 20

Several rod cells are joined by one nerve, this blurts the image formed

Question 21

What wavelength of light do cones absorb least well?

Answer 21

Blue

Question 22

What is persistence of vision?

Answer 22

When an image remains, even when the bright/intense stimulus remains

Question 23

Why do flickering lights above 5Hz appear as one light?

Answer 23

Cones take a few seconds to return to normal sensitivity. So the cones can’t desensitise in the time in between flickers