B10.5 - The Eye

Question 1

sclera

Answer 1

-white outer layer of eye
-tough
-transparent front area (cornea)

Question 2

cornea

Answer 2

-transparent
-curved surface

Question 3

purpose of cornea transparency

Answer 3

lets light in

Question 4

purpose of cornea curved surface

Answer 4

-allows rays to change direction and enter
-ensures rays focus on retina

Question 5

iris

Answer 5

-muscle
-controls size of pupil

Question 6

pupil

Answer 6

hole light enters through

Question 7

pupil in dim light

Answer 7

-enlarged = max light

Question 8

pupil in bright light

Answer 8

-iris shrinks = less light
-so light sensitive cells are not damaged

Question 9

lens

Answer 9

-clear disc = light passes
-held in place by ciliary muscles and suspensory ligaments

Question 10

lens purpose

Answer 10

-fine tunes focus of light rays
-changes their direction = focuses on retina = clear image
-

Question 11

ciliary muscles

Answer 11

contract and relax to change shape of lens
-moderate light intake

Question 12

suspensory ligaments

Answer 12

connects lens to ciliary muscles

Question 13

retina

Answer 13

-light enter and stimulates light-sensitive cells
-sends impulses to brain along sensory neurones in optic nerve
-brain = visual image

Question 14

blurry images are made by

Answer 14

light focusing in front or behind the retina

Question 15

refraction of rays

Answer 15

-cornea helps to direct rays onto retina
-rays always refract the same amount
-lens refracts light

Question 16

near sight

Answer 16

light is spreading out very strongly from close objects

Question 17

far sight

Answer 17

light from distant objects = parallel rays

Question 18

accomodation

Answer 18

process of changing shape of lens to focus on near/far objects

Question 19

focus on distant objects

Answer 19

-ciliary muscles relax
-suspensory ligaments are tight
-lens is pulled thin
-refracts light slightly as it is a distant object

Question 20

Viewing near objects

Answer 20

-ciliary muscles contract
-suspensory ligaments loosen
-lens is thicker and curved
-refracts rays strongly

Question 21

aging on eye

Answer 21

lens hardens
accommodation becomes harder
-not easy to focus on close objects

Question 22

myopia

Answer 22

short sightedness
-can see close objects but not far ones

Question 23

causes of myopia

Answer 23

-light is focused in front of retina = blurry
-lens is too curved or long eyeball
Too thick

Question 24

treatment of myopia

Answer 24

-glasses with concave lens
-spread light from distance before it reaches retina
-unfocus the light before entering

Question 25

hyperopia

Answer 25

-can focus on distant objects but not close ones -light is focused behind retina

Question 26

Hyperopia cause

Answer 26

-lens is too flat/thin -short eyeball -lens cannot refract light strongly enough

Question 27

treatment of hyperopia

Answer 27

-glasses with convex lens -brings rays together before enters eye -can focus rays onto retina

Question 28

Eye defects

Answer 28

hyperopia myopia

Question 29

contact lenses and pros

Answer 29

-placed on surface of eye -cannot be seen = better for sport -hard contacts = durable material -soft contacts = flexible and comfortable

Question 29

laser eye surgery

Answer 29

only for adults when eye stops growing -treats myopia -reduces thickness of cornea = refracts light less strongly -to treat hyperopia lasers change curve of cornea

Question 29

replacement lens treatment

Answer 29

-add another lens into eye to correct defect -1 = faulty lens is replaced by artificial lens -2 = contact lens is implanted into eye + natural lens is left in eye

Question 30

Risks of replacement lens treatment

Answer 30

-damage to retina -cataracts develop -infections

Question 31

Distant object refraction of ray

Answer 31

Light from distant object is only focused a small amount -more parallel than rays from near objects

Question 32

Hyperopia in the elderly

Answer 32

Less elastic -cannot become thick enough to focus on near objects