structure of eyes

Question 1

eye with far object

Answer 1

incoming light is parallel
ciliary muscles relax 
suspensory ligaments are tight
lens is pulled thin 
light is refracted less
light converges on the retina

Question 2

eye with near object

Answer 2

incoming light is divergent 
ciliary muscles contract 
suspensory ligaments are loose
lens becomes fat
light is refracted more 
light converges on retina

Question 3

what are sense organs?

Answer 3

groups of receptor cells responding to different stimuli

Question 4

how the eye functions to produce a focused image

Answer 4

light rays from an object enter the transparent cornea
cornea bends to refract light rays towards one another
light ray passes through pupil
elastic lens is altered in shape
brings rays to focus on retina
cells are stimulated by the light of the image and convert light energy into electrical energy
electrical in form of impulse travels along the optic nerve to the brain
brain decodes the impulses to produce sight

Question 5

what is the iris

Answer 5

muscular structure that controls how much light passes through the pupil

Question 6

what is yellow spot/ fovea

Answer 6

the most sensitive part of the retina on which objects in the centre of the field of vision are focused is called the yellow spot or fovea

Question 7

what happens when people are colour blind

Answer 7

deficient usually in red and green cones

Question 8

why are rod cells more effective in dim light

Answer 8

rod cells are more light sensitive than cone cells

Question 9

cone cells responsible for

Answer 9

each type of cone cell is sensitive to one type of light. red green and blue

Question 10

why do we have a blind spot

Answer 10

because there are no rods or cones where the retina is joined to the optic nerve. images formed on this part of the retina are not relayed to the brain. this region is therefore called the blindspot. dont notice this because one eye can cover for the over

Question 11

what is accommodation

Answer 11

the ability to change the focal length of the lens so that er can see both near and far objects

Question 12

what does accommodation rely on

Answer 12

elasticity of the lens
existence of the ciliary muscles, which are used to alter the shape of the lens
the suspensory ligaments, which transfer the effect of the ciliary muscles to the lens

Question 13

pupil or iris reflex

Answer 13

the reflex is described as the iris reflex.

Question 14

how do the iris muscles work to control pupil size

Answer 14

the iris has an antagonistic arrangement of circular and radial muscles.

Question 15

in bright light

Answer 15

light sensitive cells in the retina detect the light intensity

impulses sent along the optic nerve to the brain

brain returns impulses along a motor nerve to the circular muscles of the iris

the circular iris muscles contract whilst the radial iris muscles relax

the diameter of the pupil decreases allowing less light to decrease damage to the retina.

Question 16

cornea

Answer 16

refracts light - bends it as it enters the eye

Question 17

iris

Answer 17

controls how much light enters the pupil

Question 18

lens

Answer 18

focuses light on to the retina

Question 19

retina

Answer 19

contains light receptors

Question 20

rods

Answer 20

sensitive to dim light and black and white

Question 21

cones

Answer 21

sensitive to colour

Question 22

optic nerve

Answer 22

carries impulses from the eye to the brain.

Question 23

where has the most of the cones and rods

Answer 23

fovea in the middle of the retina

Question 24

why is the light refracted by the eye

Answer 24

refracted by the cornea and lens so the light can focus of the lens

Question 25

what is Stereoscopic vision

Answer 25

each eye captures a slightly different view and when signals from both eyes reach the brain they are superimposed and produces into one picture with depth
from this we can form 3D pictures and can judge distances well.

Question 26

short-sight

Answer 26

can see near objects clearly but not far away.This is because the lens focuses the sharpest image in front of the retina, instead of on it.

Question 27

long-sight

Answer 27

Someone with long-sightedness can see distant objects clearly, but cannot focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it.

Question 28

how can short-sightedness be fixed?

Answer 28

This is caused by the eyeball being elongated, so that the distance between the lens and the retina is too great. It can be corrected by placing a concave lens in front of the eye.

Question 29

how can long-sightedness be fixed?

Answer 29

This is because the lens focuses the sharpest image behind the retina, instead of on it. This defect is often age-related, and due to a loss of elasticity in the lens. It is corrected by putting a convex lens in front of the eye.