Question

A man who wears glasses of power 3 diopters must hold a newspaper at least 25 cm away to see the print clearly. How far away would the newspaper have to be if he took off the glasses and still wanted clear vision?

• A. Hold the paper 1m away
• B. Hold the paper 33.3cm away
• C. Hold the paper 100m away
• D. Hold the paper 2m away

Answer 1

Answer: (A)

Hold the paper 1m away

Answer 2

The virtual image formed by the lens is at the naked eye's true near point.

\ P = 25 cm

f ==$\frac { 1 } { 3 }$m = 33.3 cm

\$\frac { 1 } { 25 }$+=$\frac { 1 } { 33.3 }$

\ = – 0.01

\ q = – 100 cm

\ When the man is not wearing the glasses he should hold the newspaper 1m away for clear vision.

The answer is (1).