2 - EYES AND IMAGES

Question 1

proximal stimulus in vision

Answer 1

the light images produced by the optical apparatus of the eyes

• patterns of different light intensities and wavelengths
• patterns contain information
• enable you to perceive the world
• if no patterns in light then the light stimulating the eye will cause you to see nothing at all

Question 2

pupil

Answer 2

the small hole in which light enters the eye

called aperture in cameras

Question 3

pupillary light reflex

Answer 3

adjusts the pupil size to ensure the correct amount of light enters the eye

• low light = hole gets larger to allow more light in
• bright light = hole gets smaller to ensure not too much light gets in

Question 4

pin hole camera

Answer 4

when the hole is so small that it can create an image itself

a light-proof box with a very small hole

image is no longer sharp if it’s larger than a pin-hole

Question 5

size of hole that makes image too blurry

Answer 5

6mm

Question 6

why are lenses needed

Answer 6

when the hole is too large so the image is blurry, need lenses to sharpen the image

Question 7

name of the lenses

Answer 7

THE LENS
- behind the pupil

CORNEA

• in front of the pupil
• transparent and can see iris and pupil behind it
• space between them is filled with aqueous humour (transparent watery substance)

Question 8

vitreous humour

Answer 8

fills the space within the chamber of the eye behind the lens

transparent jelly

Question 9

focus

Answer 9

sharp image = in focus

blurry image = out of focus

Question 10

which lens has a greater focusing power

Answer 10

the cornea

• however the lens is thicker so it’s focusing power can be adjusted

Question 11

accommodative reflex

Answer 11

automatic mechanism to adjust image focus through the alteration of lens thickness

• modern cameras do this via auto focus
• this is done by changing the relative positions of the lenses instead of the thickness

Question 12

eye diagram on page 6 week 1

Answer 12

-

Question 13

retina

Answer 13

thin sheet of cells on the back surface of the eye where the image is projected (retinal image)

Question 14

how are light patterns formed?

Answer 14

some surfaces/parts of surfaces reflect more light than others

these differences create a pattern in reflected light which corresponds to the arrangement of the objects viewed

this pattern of light is projected onto retina by the optical apparatus of the eye, forming a retinal image which is upside down - the photoreceptors respond to this pattern of light

Question 15

retinal images

Answer 15

are upside down and two dimensional

• this two dimensional image must have information about 3D as the world is 3D

Question 16

‘seeing (aka visual perception) is a process carried out by the brain on the pattern of signals transmitted to it from the retina along the ganglion cell axons’ from the optic disk

Answer 16

-

Question 17

orbit

Answer 17

socket in the skull that the eye sits in

Question 18

circular tendon of zinn

Answer 18

• at the back of the socket
• pg 20 week 1 for diagram
• extraocular musckles are attached

Question 19

optic nerve leaves through the back of the orbit and passes below the frontal lobes and connects to regions in the midbrain and forebrain

Answer 19

-

Question 20

how the eye works to see

Answer 20

• ‘to form an image, you first need a source of light to shine on the surfaces of things’
• ‘when light rays strike most surfaces they are reflected in virtually all directions (except mirrors)’
• ‘this means light will reach your eye regardless of where you’re looking from’
• ‘the reflected light that reaches the eye forms an image’
• ‘this is because eyes are lightproof boxes except for one small hole (pupil)
• ‘the hole needs to be small enough - as hole gets bigger, the image gets blurry’
• ‘use lenses to sharpen image’

Question 21

how big is too big for the pupil?

Answer 21

6-7mm in diameter