the eye Flashcards
what is the part of the eye that the light will hit first
the cornea
features of the cornea
transparent - to allow light to pass through
what is the purpose of the cornea
causes all the light that passes through it to refract
what does the pupil do
its a gap in the middle of the iris that allows light to pass through to go to the lens
what does the iris do
its the coloured part of the eye
it controls hoe big/small the pupil is
what does the lens do
it bends/ refracts light
it can change its shape, which allows it to control how strongly it refracts the light, so it can focus the light directly onto the retina
what are the two types of receptor cells in the retina
rod cells
cone cells
what do cone cells do
they allow us to see in colour because they are sensitive to the colour of light
what type of light do cone cells not work well in
low light
what do rod cells do
only allow us to see in black and white so work better in low light
why cant you see colours when its dark
its only the rod cells that are working
what does the optic nerve do
takes all the impulses generated by receptor cells and transmits them to the brain
what is the fovea
a spot on the retina where there are only cone cells
it helps to see as clearly as possible
What happens to the eye when looking at a bright light
the pupil is constricted
circular muscles contract
radial muscles relax
what happens to the eye when looking at a low light
the pupil dilates
circular muscles relax
radial muscles contract
why does the pupil constrict in a bright light
bright light can cause damage to the retina
what happens to the lens when the eye is looking at a close object
it becomes short and fat so it can be more curved
this means it can refract light more strongly
what happens to the ciliary muscles and suspensory ligaments when looking at a close object
ciliary muscles contract, causing the suspensory ligaments to slacken so they are no longer pulling tight on the lens
this means the lens can return to its fat shape
what happens to the lens when looking at a distant object
it stretches
how does the lens stretch when looking at a distant object
the ciliary muscles relax, pulling away from the lens so the suspensory ligaments will tighten
When looking at a distant object, which part of the eye refracts the light the most
the cornea refracts the light most of the way, so the lens doesn’t have to do much, which is why the lens can stretch.
what is the part of the retina that the light should be focused on
the fovea
what does long sighted mean
the eye is unable to focus on nearby objects
what type of lens do glasses contain to fix long sightedness
convex lenses which add refracting power
what type of lens do glasses contain to fix short sightedness
concave lenses which refract light outwards to counteract the lens which is over refracting the light
