Lecture 7- physics of the eye Flashcards
What is refractive index crucial for?
image formation
What is the cornea?
extremely thin
miniscus lens
What does the retina do?
image forming surface
What can optical surfaces can be approximated to?
a single thin lens, where refraction happens and able to focus light on retina
What is a retina formed of?
receptors
What are the different refractive powers that the differemnt surfaces of the human eye have?
a
What ids the lens average in terms of refractive indices?
highly inhomogenous
What are the 3 surfaces of the eye?
cornea
front surface of lens
back surface of lens
In image formation, When you have a distant object (do) what are the rays like?
parallel into the eye- flat
and focused onto the retina
The distant object is large
What is the lens to retina distance like?
lens to retina distance stays the same= 2.0cm
What is the eyes accomadation when viewing distant objects?
Most relaxed- unaccomadated
What happens when the eye is accomodated?
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
What are the compensation in the eye to minimise aberrations?
- The gradient index of the crystalline lens will minismise spherical aberraations
- chromatic aberrations- minimised by the specific arrangement of cones on fovea
Where is the highest visual acuity of the retina?
on the fovea- and the fovea lies in the region where there are no S cones (blue)
Why is there only L and M cones in the centre of the retina- Normal Colour vision?
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
