Study the given diagram and answer the questions that follows: i. Which defect of vision is represented in this case? Give a reason for your answer. ii. What could be the two causes of this defect? iii. With the help of a diagram showing how this defect can be corrected by the use of the suitable lens.

Question

Philoid · Accepted Answer

i. The figure represents Hypermetropia. Hypermetropia or far sightedness is an eye defect in which a person is not able to see things placed closer to the eye. The light rays coming from the object placed between near point & the point of least distance of distinct vision, after refraction from the eye lens converges to a point beyond the retina. This implies that the image is formed beyond the eye thus creating a blurry image. In such cases the focal length of the eye lens increases.

ii. Some of the causes of hypermetropia are:

•Low converging power of eye lens because of weak action of ciliary muscles.

•Abnormal shape of the cornea

iii. The defect can be corrected by using the convex lens. To bring the image on retina a double convex lens is used. The double convex lens converges the light rays coming from the object in front of the eye lens. In other words, the convex lens creates an image of the object at the near point. Now this image acts as an object for the eye lens and thus forming an image on the retina.