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Image Formation - Coggle Diagram
Image Formation
combined refractive powers of the
cornea
and lens
Cornea Refraction
distant object:
parallel
rays hit cornea
light that enters perpendicular → straight to the retina
angles other than perpendicular are bent → converge on the back of the retina
distance from refractive
surface
to the point of
convergence
: focal distance
depends on
curvature of the cornea
tighter curve, shorter focal distance
reciprocal (in m)
diopter :muscle:
unit of measurement of
refractive power
cornea: 43 diopters
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Lens accommodation
lens contributes ~dozen diopters to form image of distant object
most significant contribution
images of objects located closer than 9m
near objects, the light rays originating at a point are
not parallel
greater refractive power required to bring them into focus on the retina
change the shape of the lens
accommodation
ciliary muscle contracts and swells in size → making the area inside the ring smaller :doughnut:
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(+ additional contributions)
Pupillary Light Reflex
the pupil 💡 contributes by continuously adjusting for different light levels
involves connections between the
retina
and neurons in the
brain stem
(which control the muscles that constrict the pupils at high light)
consensual
shining a light into only one eye causes the constriction of the pupils of both eyes.
benefit
increase in the depth of focus (distant objects appear to be less out of focus)
How are images formed by the eye?