Why is iris of eye called diaphragm of eye?

Explanation

### Step-by-Step Solution:

1. **Definition of Iris**: The iris is the colored part of the eye that surrounds the pupil. It is responsible for controlling the size of the pupil.

2. **Function of the Iris**: The primary function of the iris is to regulate the amount of light that enters the eye. It does this by adjusting the size of the pupil.

3. **Response to Light Conditions**:
- In bright light conditions, the iris constricts (closes) the pupil to reduce the amount of light entering the eye. This helps to protect the retina from excessive light exposure.
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