Chapter 18, Problem 70A

To determine

The condition in which the focal length of the eye is too short to focus light on the retina.

Answer to Problem 70A

The condition in which the focal length of the eye is too short to focus light on the retina is nearsightedness.

Explanation of Solution

Introduction:

In case of a normal eye, the reflected light from object enter the eye through the cornea, and then it passes through the eye’s pupil and falls on the lens. The lens focuses the light rays on the retina. The photo receptors in the retina provide signal to the brain, and the brain responses to the signals and the image of the object is formed and the person can able to see the object. Any kind of changes or irregularities in the eye, a blurred image of the object will be formed.

Due to environmental and genetic factors, the eyes of some persons are to some extent longer than that of the normal eye.

The focal length of the eye is too short for some people to focus the light on the retina.

The light falling on lens get focussed at a point in front of retina causing the formation of blurred image of the distinct objects.

In this defect of vision, the person will not be able see far distance objects clearly but the person will be able to see the nearby object clearly.

Hence, the condition in which the focal length of the eye is too short to focus light on the retina is nearsightedness (myopia).

Conclusion:

Thus, the condition in which the focal length of the eye is too short to focus light on the retina is nearsightedness.