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Science exam eye

human vision & optical systems

QuestionAnswer
light enters your eye through the _______ pupil
surrounding the pupil is a coloured muscle calle the _______ iris
the iris's job is to: change the size of the pupil so the right amount of light will go in
when it is dim, the iris _____ dilates (expands)
when it is bright, the iris ________ contracts
covering iris and pupil is the __________ cornea
cornea is: a transparent tissue that lets light through but holds the eye together
white part of eye is called the _____ sclera
behind the pupil is a ____________ that is flexible enough to change its shape convex lens
light rays pass though the lens and focus onto the screen at the backk of the eye, called the _____ retina
cells in the retina convert the light rays into electrical signals which are sent to the brain through the: optic nerve
as light rays contact the eye...: the curved cornea causes them to refract so that the image can form on the retina
the ______ is adjusted by muscles to do the final bit of focussing so that the image iwll form at just the right distance to appear on the retinca lens
the _________ does most of the focussing and the _________ does the rest of the focussing cornea, lens
if the object is far away, the lens is _________ thinner
if the object is close, the lens is _______ thicker
Where the optic nerve enters the retina is a small area where there are no light-sensing cells, called the: blind spot
_____________ are used to detect shades of light and dark. In low light, these cells are the main ones we use to see Rod cells
__________ detect colour. There are three types, which detect primarlily the three primary colours, red, green, and blue (as well as their corresponding secondary colours). Cone cells
In normal vision, the muscles change the shape of the _____ so that light from near and far objects focuses in the right place -on the retina lens
If a person is near-sighted, they see near objects fine but have difficulty focussing distant object. This is normally because: the eye has become elongated, so the light rays from distant objects converge in front of the cornea
Near-sightedness is fixed with: a concave lens
Far-sightedness is fixed with: a convex lens
If a person is far-sighted, they see distant objects fine but have difficulty focussing nearby objects. This is normally because: the eye has become shorter, so the light rays from distant objects do not converge in time they reach the cornea
when people get older, people usually get: near-sightedness
when people get older, people have eye problems because: the muscles are weaker
If a person has astigmatism, the __________ has a distorted shape so that it's images are focussed on more than one place on the _____________ cornea,retina
astigmatism is corrected with: a special kind of glasses or contact lenses
blindness vision problem (no light, no colour (or just certain colours), any type of vision problem)
Created by: jlarose on 2008-11-15



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