Question

Fill in the blanks:
The power of accommodation in a human eye is the ability of the (i)____________to adjust its (ii)_______.
A. (i) pupil
     (ii) weight
B. (i) pupil
    (ii) diameter
C. (i) retina
    (ii) focal length
D. (i) lens
     (ii) distance from the retina human

Answer 1

Hint: The accommodation of the eye is the process by which ciliary muscles of the eye function to change the focal length of the eyes so that the image is formed on the retina. The focal length will vary for near and distant objects.

Complete step by step solution:
The various parts of the human eye work simultaneously to help us in the process of vision. A series of operations occur from the point of light rays entering the eye to the image formation. One of these processes is the power of accommodation of the eye. The figure given below represents image formation in the retina of the normal human eye in various situations.

We know that the ability of an eye to change its focal length is known as accommodation. A nearby object can be focused at a farther distance, the eye accommodates the light by assuming a lens shape in which the ciliary muscles relax and assumes a flatter shape. By reducing the focal length more refraction of light can occur, image is formed upon the retinal surface. For nearby objects, the ciliary muscles contract and the lens changes to a convex shape. On increasing the curvature of the lens focal length decreases.
The power of accommodation of the human eye is the ability of the retina to adjust its focal length. Therefore option C is the correct choice.

Additional information:
The unit for the power of lens is diopter. Diopter is the inverse of focal length. For a person with normal vision power of accommodation is 4 diopters.
\[\text{Diopter = }\dfrac{\text{1}}{\text{focal length}}\]

Note: Since it is a biological function, everyone doesn’t have the same power of accommodation. That’s why we are using spectacles to reduce the problems with the power of accommodation. Short-sightedness and long-sightedness are some of the problems arising due to the less power of accommodation of the eye.