Question

A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is

• A.
  • 0.5 D
• B. – 1.0 D
• C. – 10 D
• D.
  • 4.0 D

Answer 1

Answer: (B)

– 1.0 D

Answer 2

$f = - \mspace{6mu} d = - \mspace{6mu} 100\mspace{6mu} cm = - \mspace{6mu} 1\mspace{6mu} m$

$\therefore P = \frac{1}{f} = \frac{1}{- 1} = - \mspace{6mu} 1\mspace{6mu} D$