Lecture 7- physics of the eye

Question 1

What is refractive index crucial for?

Answer 1

image formation

Question 2

What is the cornea?

Answer 2

extremely thin

miniscus lens

Question 3

What does the retina do?

Answer 3

image forming surface

Question 4

What can optical surfaces can be approximated to?

Answer 4

a single thin lens, where refraction happens and able to focus light on retina

Question 5

What is a retina formed of?

Answer 5

receptors

Question 6

What are the different refractive powers that the differemnt surfaces of the human eye have?

Answer 6

a

Question 7

What ids the lens average in terms of refractive indices?

Answer 7

highly inhomogenous

Question 8

What are the 3 surfaces of the eye?

Answer 8

cornea
front surface of lens
back surface of lens

Question 9

In image formation, When you have a distant object (do) what are the rays like?

Answer 9

parallel into the eye- flat
and focused onto the retina
The distant object is large

Question 10

What is the lens to retina distance like?

Answer 10

lens to retina distance stays the same= 2.0cm

Question 11

What is the eyes accomadation when viewing distant objects?

Answer 11

Most relaxed- unaccomadated

Question 12

What happens when the eye is accomodated?

Answer 12

lens change shape- changing the power- allows for the eye to focus the object closer to us- the lens is made thicker and more converging by the action of the ciliary muscle

Question 13

What are the compensation in the eye to minimise aberrations?

Answer 13

• The gradient index of the crystalline lens will minismise spherical aberraations
• chromatic aberrations- minimised by the specific arrangement of cones on fovea

Question 14

Where is the highest visual acuity of the retina?

Answer 14

on the fovea- and the fovea lies in the region where there are no S cones (blue)

Question 15

Why is there only L and M cones in the centre of the retina- Normal Colour vision?

Answer 15

By having L and M cones in the retina-their spectral seperation is 28nm- small- fire signal in brain- shraply in focus however if blue cones fire- there is a 100nm differenece hence

Question 16

How is the eye developed?

Answer 16

eye has developed so the centre of the retina is void of blue cone- hence increasing VA.- Preventing influence of blue cones

Question 17

What happens to the pupil in dim light?

Answer 17

pupil dialation

Question 18

What happens to the pupil in bright luight?

Answer 18

pupil constriction