The Eye Flashcards
Go revise a diagram
NOW
How does the eye focus?
The cornea and the lens converge light rays from objects and focus them to the retina
What is accommodation?
The focusing of the eye
What happens during DISTANT accomodation?
Ciliary muscles relax
Lens pulled thin/tight/flat
Suspensory ligament taut (pulls out lens)
What happens during NEAR accomodation?
Ciliary muscles contract
Lens becomes rounded/fat
Suspensory ligament loose/relaxed
What two sorts of receptor cell does the retina contain?
Rods and Cones
Rods and Cones are examples of
Receptor cells in the retina
Rods are
Sensitive to quite dim light, they only let you see in black and white
Cones…
give colour vision, but only in bright light
How is an image obtained in the brain?
- Light falls onto receptor cells in the retina and a message is sent along the optic nerve to the brain
- The brain sorts out the messages and makes an image
Where are the receptor cells packed closely?
In the fovea
What does the cornea do?
Bends and refracts most of the light rays so that they are focused on the retina
What happens to light rays of a nearby object?
-Use finger as an example?
They are bent inwards a lot
What happens to light rays of a far object?
Since the rays are almost parallel, they will not bend a lot
How much does a fat/thin lens bend the light
A fat lens will bend light more
A thin lens will bend light less
What causes long sighted eyes?
Weak lenses, when the light cannot be bent enough (thin lenses) to focus on the retina and end us focusing behind it
What causes short sighted eyes?
When the light rays are bent too much (fat lenses) so that it ends up focusing too far in front of the retina
Correction for long sight?
Wearing convexed lenses
Correction for short sight?
Wearing concaved lenses
