Lecture 7 - Physics of the eye Flashcards
Where is image formed in eye
Retina
What is refractive indices crucial for
Image formation
Where does the largest change in refractive index occur
Cornea
What does lens provide
Remaining power needed to produce an image on retina
What happens when focusing on distant object
Parallel rays focused onto retina
Distant between object VERY LARGE
Lens to retina distance is same
Eye is UNACCOMMODATING - most relaxed when viewing distant objects
Distance from where rays refract to back of eye is always CONSTANT - eye same shape
What happens when focusing on near object
Distant between near object VERY SMALL
Lens to retina distance is same
Eye is ACCOMMODATED - lens made thicker and more converging by action of ciliary muscles surrounding it
What happens during acommodation
Lens changes shape and power = focus objects closer to us on retina - focusing on near object
What minimises spherical aberrations
The gradient index of crystalline lens
Lens in eye - homogeneous refractive index
What minimises chromatic aberrations
Specific arrangement of cones in foveal area
s cones - scarce in central fovea
What is chromatic aberration
Aberration due to different wavelength found in white light
What is the role of the pupil
Controls amount of light entering eye
How is the amount of light entering the eye controlled
By the iris - constricts or dilates pupil
How does the iris reduce amount of light entering eye
Muscles in iris - constricts size of pupil - restricts amount of light entering eye
When does it close
When a lot of light present
When does it open
When insufficient amount of light
