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?

Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.

(a) Is she short-sighted or long-sighted?

(b) What type of lenses-converging or diverging-would an optician prescribe for her?

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?

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.

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