The Eye! Flashcards
What is the job of the iris?
The iris has muscles, which contract and relax to alter the size of the pupil and controls the amount of light entering.
What does a round fat lens mean?
The muscles are contracted and looking at something up close. Light is being refracted more.
What does a thin long lens mean?
The muscles are relaxed and looking at something far away. Light is being refracted less.
What do the ciliary muscles do?
Contract to make the lens round and relax to make the lens flat.
What is the cornea and what does it do?
It is a transparent layer and does some focussing.
What does the lens do?
It changes shape to focus light on the retina.
What does the iris do?
It is the coloured part of the eye, it changes the size of the pupil.
What is the pupil and what does it do?
It is a hole that lets light through.
What is the retina and what does it do?
It is at the back of the eye, it is covered in light-sensitive cells.
What are the suspensory ligaments and what does it do?
They are ligaments that pull the lens flat.
What is short sightedness? What causes it?
Can’t see distant objects. Image is formed inside the eye (in front of the retina). It is caused by the eyeball being too large or the cornea and lens being too strong. Muscles cannot make the lens thin enough.
What is long sightedness? What causes it?
Can’t see close up objects. Image is formed behind the retina. Caused by the eyeball being too small or the cornea and lens being too weak.
Which type of lens corrects short sightedness?
A diverging lens (w/ negative power)
Which type of lens corrects long sightedness?
A converging lens (w/ positive power)
