Question

Briefly explain the power of accommodation.

Answer 1

Hint:Human eye plays a vital role in survival. It is an important part in the sensory nervous system of all the organism. It makes the things or the environment visible to the human. Rods and cone cells in the retina help in the process of perception of light and the vision.

Complete answer:
Accommodation is defined as the ability of the eye lens to view the different objects clearly either near or far away from it by adjusting its focal length. Whereas the power of accommodation is specified as the variation of its power to focus the far and near objects. Power of accommodation lies to the certain limit below which the focal length cannot be adjusted.

This process is mainly done by the lens and the ciliary muscles in the eye. The ciliary muscles in the eye contract and expand in order to focus the different objects on the retina. It modifies the lens curvature to change the focal length of the different objects it focuses. When the nearby objects are viewed, the ciliary muscle contracts, so the lens becomes thicker and focal length decreases. When the far objects are viewed the ciliary muscles expand and the lens becomes thinner to make increase in focal length. The power of accommodation of the normal healthy man is 4D .Diopter is the unit of the power of the lens.

Note: The minimum distance at which the objects can be seen clearly is called the near point of the eye and the maximum distance at which the objects can be seen clearly is known as the farthest point of the eye.