The diaphragm in the camera is similar to what part of the eyes?

Analysis

The question asks us to identify the part of the human eye that performs a function analogous to the diaphragm of a camera.

Concept Explanation

To understand this, we must look at the function of both components:

• Camera Diaphragm (Aperture): This is an adjustable opening that controls the amount of light entering the camera lens. By opening wider or closing tighter, it regulates the intensity of light reaching the film or sensor.
• Human Eye: The eye also needs to regulate the amount of light entering it to protect the retina and ensure clear vision under different lighting conditions.

Step-by-Step Solution

1. Cornea (Option A): This is the transparent front part of the eye that acts as a fixed lens, helping to focus light. It does not control the amount of light.
2. Lens (Option B): The eye lens changes shape to focus light onto the retina (accommodation). It is responsible for focusing, not for regulating light intensity.
3. Ciliary muscle (Option C): These muscles control the shape of the eye lens to allow for focusing at different distances. They do not control light intensity.
4. Iris (Option D): The iris is the colored part of the eye. It contains muscles that adjust the size of the pupil (the hole in the center). By changing the size of the pupil, the iris controls the amount of light that enters the eye, exactly like the diaphragm of a camera.

Conclusion

Since the iris regulates the light entering the eye by adjusting the pupil size, it is the direct equivalent of the camera's diaphragm.

Exam Tip

Think of it this way: "Iris = Intensity." Whenever you see a question about controlling the amount of light in the eye, always look for the Iris. If the question asks about focusing light, look for the Lens.