alleryThe function of the iris is to:
AFocus the image
BControl the size of the pupil
CConvert light to signals
DCarry signals to the brain
Answer & Solution
Correct answer: B. Control the size of the pupil
The iris is the colored, ring-shaped muscular diaphragm located behind the cornea. Its primary biological function is to regulate the amount of light reaching the retina.
1. **Mechanism**: The iris consists of two sets of muscles: the sphincter pupillae (which constricts) and the dilator pupillae (which expands).
2. **Action**: These muscles adjust the diameter of the **pupil**, the central opening of the eye.
3. **Light Regulation**:
- In bright light, the iris constricts the pupil to prevent overexposure.
- In dim light, the iris dilates the pupil to allow more light to enter.
Therefore, the correct function of the iris is to **control the size of the pupil**.
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