Question

A student sitting in the last row of the classroom is not able to read the writing on the blackboard.
(I) Name the type of defect he is suffering from.
(II) How can these defects be corrected?

Answer 1

Hint:The child is not able to read properly; it implies that he is suffering from eye problems. There are many common eye defects like myopia, hypermetropia, presbyopia etc. We need to look at them in detail now.

Complete step by step answer:
(I) The child is not able to read the writing on the blackboard. This means he is suffering from nearsightedness. It is a condition in which close objects appear clearly, but far ones do not appear sharp. This type of eye problem is called myopia. The cause of myopia is when the shape of the eye causes light rays to bend incorrectly, focusing images in front of the retina. Image is formed at some distance before the retina but not at the retina.
(II) myopia can be corrected by using a diverging lens that is concave. Since the image is being formed before the retina so the concave lens diverges the rays passing through it and then the image is formed on the retina.
Additional Information:
 Myopia may develop gradually or rapidly and tends to run in families. Hypermetropia is another eye problem in which a person can see far away objects clearly but is not able to see nearby objects distinctly.

Note:Concave lenses diverge the rays so we use the concave lens in myopia which diverges the rays. In our eye, there is a convex lens which converges these diverging rays onto the retina.