Question

The amount of light entering in the eye is controlled by:

• A. ciliary muscles
• B. eye lens
• C. pupil
• D. cornea

Hint:

Remember: The pupil controls light entry, the lens focuses the image, and the ciliary muscles adjust the lens shape.

Answer 1

The Correct Option is C

The pupil is a vital part of the human eye that controls the amount of light entering the eye. It appears as the black circular opening in the center of the iris and functions similarly to the aperture of a camera. The size of the pupil is automatically adjusted by the iris, which is the colored part of the eye surrounding the pupil. \smallskip 1.
Role of the Iris:

The iris contains muscles that contract or relax to change the size of the pupil depending on the lighting conditions.
In
bright light, the iris contracts, making the pupil
smaller to reduce the amount of light entering the eye and protect the sensitive retina from excessive light.
In
dim light, the iris relaxes, causing the pupil to
enlarge (dilate) and allow more light to enter, helping improve vision in low-light conditions.
\smallskip 2.
Distinction from Other Eye Structures:

While the
ciliary muscles play a crucial role in adjusting the shape of the eye's
lens for focusing on near or distant objects (a process called \textit{accommodation}), they are not responsible for controlling light entry.
The
cornea is the transparent, curved front surface of the eye that helps in
refracting (bending) incoming light toward the lens, but it does not regulate the amount of light.
The
pupil, therefore, has the
specific role of regulating how much light enters the eye, ensuring that the retina receives an appropriate amount for clear vision without damage.
\smallskip In conclusion, the pupil, by changing its size with the help of the iris, specifically controls the entry of light into the eye. This function is distinct from other parts like the ciliary muscles and cornea, which have different roles in vision.