the eye and the visual stimulus

Question 1

what is the iris

Answer 1

loose open muscular membrane in the centre forming the pupil

Question 2

what is the pupil

Answer 2

centre opening of iris that allows light to enter

Question 3

why does the pupil change size

Answer 3

it varies with light intensity and size

Question 4

what is the cornea

Answer 4

domelike optical structure covering the pupil and iris and is the refracting element of the eye

Question 5

what is the sclera

Answer 5

tough fibrous outer coat that provides structural strength

Question 6

what is the conjuctiva

Answer 6

covers the sclera and extends over the eyelids

Question 7

what is the tear film

Answer 7

it covers the cornea and conjuctiva

Question 8

what is the limbus

Answer 8

where cornea and sclera meet

Question 9

what is the punctum lacrimalis

Answer 9

opening to the tear drainage system

Question 10

lacrimal caruncle

Answer 10

small white/pink raised area in the corner of the eye

Question 11

what is the aqueous humour

Answer 11

clear fluid in the anterior chamber

Question 12

what is a lens

Answer 12

crystalline transparent structure attached to the ciliary body and suspended by thin fibrils

Question 13

how does the lens shape change

Answer 13

by action of the ciliary muscle

Question 14

what is the choroid

Answer 14

vascular layer that sits between retina and sclera. It also provides nutrients to the eye

Question 15

what is the vitreous

Answer 15

clear jelly like structure which sits behind the lens

Question 16

what is the retina

Answer 16

light sensitive organ containing photoreceptors

Question 17

what is the fovea

Answer 17

central retinal pit that contains only cones

Question 18

what is the macula

Answer 18

surrounds the fovea and appears yellow due to pigment

Question 19

what is the visual and optical axis

Answer 19

visual axis- line drawn from the fovea to the point an eye is gazing at
optical axis- line through the optical centre

Question 20

what is light

Answer 20

a wave and stream of particles

Question 21

what is a quantum

Answer 21

unit of energy

Question 22

what is light as waves used for

Answer 22

to explain diffraction, interference and polarisation

Question 23

what is light as rays used for

Answer 23

to understand the optical pathway through systems

Question 24

what is light as quanta used for

Answer 24

to understand processes in the photoreceptors

Question 25

what is frequency

Answer 25

number of cycles per sec

Question 26

what is the energy equation

Answer 26

E= h*v h= planks constant(6.626 x 10^-34) joules per sec v= frequency in Hz OR E+h*c/λ c=speed of light λ= wavelength

Question 27

what is the wavelength equation

Answer 27

λ=c/v c=speed f light in a vacuum v=frequency

Question 28

what is the relationship with frequency and wavelength

Answer 28

the lower the frequency the longer the wavelength

Question 29

what is the unit for wavelength

Answer 29

nanometers

Question 30

what is radiometry

Answer 30

measurement of the quantity of energy of the electromagnetic radiation using physical energy units and radiometric devices.

Question 31

what Is photometry

Answer 31

measure of visible radiation (usually between 380-750nm)

Question 32

What is luminance flux/power (F) and what is it measured in

Answer 32

total amount of light emitted by a source in all directions- its photometric unit is in unit of lumen lm and its radiometric is radiant power or flux joules/sec

Question 33

what is luminous intensity(l)

Answer 33

Measure of light from a solid angle from a point source in a particular direction- its photometric unit is in candela cd(one lumen=one candela) and its radiometric unit is radian intensity watts

Question 34

what is luminance and its units

Answer 34

amount of light coming off an extended surface in a particular direction- its photometric unit is candelas/m2 and its radiometric is in radiance watts

Question 35

what is illuminance and what are its units

Answer 35

amount of luminance power falling onto an area of a certain surface- its photometric unit is unit of lumens(lumens/ m2) and its radiometric unit is irradiance Ee

Question 36

How does the visual response begin

Answer 36

When light passes into the rods and cones in the eye

Question 37

what does the amount of light that falls on the retina depend on

Answer 37

it depends on the luminance of the stimulus, the optical transmission of the eye(how much light gets into the retina) and the area of the pupil

Question 38

what is the unit for the amount of light reaching the retina

Answer 38

Troland

Question 39

How do you work out the retinal illuminance

Answer 39

E ret= L(luminence) x a(pupil area)

Question 40

what is brightness

Answer 40

perception of the amount of light (also depends on the surround)

Question 41

what is the lightness

Answer 41

perception of the surface colour