Can You Make Your Eyes Change Size?

The pupil's of your eyes automatically change size many times throughout the day. They do this to control the amount of light entering the center of your eye. Try this experiment and check out how the pupils dilate and constrict.

Materials Needed:

penlight
mirror or friend.

Procedure

Sit in a semi-darkened room for a few minutes with both eyes opened.
After a few minutes look in the mirror and observe the size of your pupils. (The colored part of your eye.)
While continuing to look in the mirror, take the penlight and shine it into your eyes for one second. Then immediately shut the light off.
Observe the size of your pupils.

What Happened?

The pupils will constrict and become much smaller after shining the light into the eyes.

Why

The pupil controls the amount of light entering the center of your eye. This is done so that the rods and cones in the back of your eye are protected from too much light. In dim light the pupils open wider or dilate so that you will be able to see better.

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