the eye Flashcards
what are the two receptor cells in the retina
cone cells and rod cells
what are cone cells
sensitive to colour of light and only work in bright light
what are rod cells
detects differences in colour intensity (brightness) and works well in poor light
what is the retina
light sensitive cells at the back of the eye that detect light and interprets information to form an image
what is the cornea
clear colourless covering that causes focusing of light (refracts light onto the retina)
what is the lens
transparent surface in front of eye that similarly to the cornea, reflects light on to retina
what is the optic nerve
bundles of neurones that send nerve impulses to brain
what is the iris
muscles that surround the pupil that contract or dilate the pupil
controls the amount of light entering the eye
what is the pupil
where light enters the eye
what do ciliary muscles do
hold lens in place and control shape that allows focus on objects nearer or further away
what is accommodation
the ability of the lens to change shape to focus on objects at different distances
what happens when light focuses on a near object
DIVERGING LIGHT RAYS
lens becomes thicker and fatter
light rays have to bend a lot
ciliary muscles contract
what happens when light focuses on a distant object
PARALLEL LIGHT RAYS
lens becomes skinnier and longer
light rays need less bending to reach the retina (less refracting)
ciliary muscles relax
how is short sightedness formed
(opposite for long sightedness)
eyeball is too long
OR
cornea is too curved and bends rays more than they should
how to correct short sightedness
DIVERGING LENS
spreads out rays before they reach the eye
