eye optics Flashcards
what does the cornea and lens do?
they focus light on the retina
when does the pupil constrict?
when light passes into it
when does the pupil dilate (get bigger)
when it is dark
full depth of field
happens when our pupils are constricted, where everything we see is with the same focus
shallow depth of field
happens when our pupils are dilated, where some things appear to be more in focus than others
what is the issue with only using the pupil to focus light?
when the pupil is constricted we get a limited amount of light through the hole and when it dilates there is more light that comes through but the image is blurry
How do we fix the issue of only using the pupil, so that the images we receive are bright and clear?
by using refraction
why does our cornea refract light strongly in air?
because our cornea is made of collagen and there is a big difference between the refractive indices of collagen and air
why is the refraction weaker in water
because the refractive indices of collagen and water are very similar to one another
what makes the incoming light refract to a focal point?
the lens itself is convex, meaning that the middle of it is thicker than the edges, which are thinner. tis difference allows the light to bend a specific way so that the beams bend to the same focal point
Accomodation
we can accommodate/alter the angles at which the light hit the lens by changing the shape of the lens, by making it rounder or more narrow
how is the lens in the eye rounded to bring a closer object into focus
the parasympathetic signals to contract the smooth ciliary muscles, reducing tension of the zonules making the lens rounder
near point of accommodation
the closest point an object can be where the individual can adjust their lens to bring it into view
presbyopia
the condition of the stiffening of the lens, making it harder to adjust to closer objects- happens with age
hyperopia
this is known as far-sightedness where the focal point falls behind the retina
