Iris and pupil
The adjustable opening of the eye.
A camera opening
A camera has an opening that can be made wider or narrower. The eye has a similar opening, the pupil, behind the cornea.
If the pupil is made wider, what happens?
What this lesson covers
The idea
The iris, a dark muscular diaphragm behind the cornea, controls the size of the pupil, which regulates and controls the amount of light entering the eye.
A camera opening
A camera has an opening that can be made wider or narrower. The eye has a similar opening, the pupil, behind the cornea.
If the pupil is made wider, what happens?
- More light enters the eye
- Less light enters the eye
- The same amount of light enters the eye
Change the pupil
Move the slider to change the size of the pupil. Watch the bar for the light entering the eye.
The iris at work
The iris is a dark ring of muscle. By changing the size of the pupil, it controls how much light goes into the eye.
The iris, a dark muscular diaphragm behind the cornea, controls the size of the pupil, which regulates and controls the amount of light entering the eye.
Notes
The iris, a dark muscular diaphragm, controls the size of the pupil, which regulates the amount of light entering the eye.
Check yourself
Which part of the eye controls the size of the pupil?
The iris is…
What does the pupil do?
The pupil is made wider. The amount of light entering the eye…
- The retina. The retina is the screen with light-sensitive cells. The iris controls the size of the pupil.
- The cornea. The cornea is the transparent bulge on the front of the eye. The iris controls the size of the pupil.
- The iris — correct. Yes!
- a dark muscular diaphragm behind the cornea — correct. Yes!
- a thin transparent membrane that forms the bulge on the front of the eyeball. That describes the cornea. The iris is the dark muscular diaphragm behind it.
- a delicate membrane with an enormous number of light-sensitive cells. That describes the retina. The iris is a dark muscular diaphragm.
- It forms the image of the object. The image is formed on the retina. The pupil regulates the amount of light entering the eye.
- It regulates and controls the amount of light entering the eye — correct. Yes!
- It carries signals to the brain. The optic nerves carry signals to the brain. The pupil regulates the amount of light entering the eye.
- decreases. A wider pupil lets in more light, not less.
- stays the same. The pupil regulates and controls the amount of light entering the eye, so changing its size changes the amount of light.
- increases — correct. Yes!