Complete the following sentences:

(a) A short-sighted person cannot see _______ objects clearly. Short-sightedness can be corrected by using

_______ lenses.

(b) A long-sighted person cannot see _______ objects clearly. Long-sightedness can be corrected by using

_______ lenses.

A man can read the number of a distant bus clearly but he finds difficulty in reading a book.

(a) From which defect of the eye is he suffering?

(b) What type of spectacle lens should he use to correct the defect?

A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.

(a) Name the type of defect he is suffering from.

(b) How can this defect by corrected?

What are the two most common defects of vision (or defects of eye)? How are they corrected?

Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help ?