| Question |
 |
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| Answer |
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| 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) |
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