The part of the human eye that does similar work as the diaphragm of a camera lens is the

Analysis

The question asks us to identify the part of the human eye that functions like the diaphragm of a camera. To solve this, we need to understand the function of a camera diaphragm and compare it to the structures of the human eye.

Concept Explanation

• The Camera Diaphragm: In a camera, the diaphragm is an adjustable opening (aperture) that controls the amount of light entering the camera lens. When it is bright, the diaphragm closes to let in less light; when it is dim, it opens wider to let in more light.
• The Iris: In the human eye, the iris is the colored part of the eye. It contains muscles that control the size of the pupil. By expanding or contracting, the iris regulates the amount of light that enters the eye, performing the exact same function as the camera diaphragm.
• The Pupil: This is the hole or opening itself (the aperture), not the mechanism that controls the size of the opening.
• The Ciliary Muscles: These control the shape of the eye lens to focus on objects at different distances (accommodation), not the amount of light.
• The Retina: This acts like the camera's film or sensor, where the image is formed.

Step-by-Step Solution

1. Identify the function: We are looking for the part that regulates light intensity.
2. Evaluate the options: • Ciliary muscles: Responsible for focusing (accommodation). • Pupil: The aperture itself, not the control mechanism. • Iris: The muscular ring that adjusts the size of the pupil to control light entry. • Retina: The light-sensitive screen where the image is captured.
3. Conclusion: Since the iris acts as the adjustable shutter/diaphragm that controls the size of the pupil, it is the correct anatomical equivalent to the camera diaphragm.

Identifying the Answer

This aligns with our biological understanding of the eye's anatomy.

Exam Tip

Think of the eye as a camera:

• Iris = Diaphragm (controls light).
• Pupil = Aperture (the hole).
• Lens = Camera Lens (focusing).
• Retina = Film/Sensor (image capture).