The Eye Flashcards
When the ciliary muscles relax what happens to the lens?
It becomes thinner and flatter
What happens to the lens when the ciliary muscles contract?
It becomes fatter and more spherical
What does the retina do?
Images are formed on the retina by light sensitive cells.
The cells send signals to be interpreted by the brain
What does the lens do?
Connected to the ciliary muscle by the suspensary ligaments.
It changes shape to focus light from objects at varying distances
What causes SHORT sight?
A too long eyeball or too powerful cornea and lens.
What causes LONG sight?
A too short eyeball or not powerful enough lens.
How is long sightedness corrected?
> using a converging lens that helps the light rays to converge in the right place.
How is short sightedness corrected?
> using a diverging lens to diverge the light rays slightly, meaning that they are focused on the retina
What is the main similarity between the camera and the eye?
They both create an image that is:
>real
>inverted
>diminished
What are the comparisons between the focusing of the eye and a camera?
> camera has CONVERGING lens with a fixed focus controlled by the position of the lens
> the eye has a CONVERGING lens with variable focus controlled by size and shape of lens by contraction of ciliary muscle
What are the comparisons between the eye and a camera in the way an image is formed?
> in a camera the image is focused on film/CCD
> in eye is focused on light sensitive cells in the retina
What are the comparisons between how the brightness is controlled in the eye and a camera?
> the eye is controlled by iris and pupil
> camera is controlled by aperture and diaphragm
Why does a short eyeball cause long sightedness?
> light rays are focused after the retina
> lens is unable to converge the rays enough
How does laser eye surgery work?
> a laser ( very intense and focused light-monochromatic) is used to burn off a thin layer of the lens.
