Question

A man can see only between $75cm$ and $200cm$. The power of lens to correct the near point will be

• A. $+8/3D$
• B. $+3D$
• C. $-3D$
• D. $-8/3D$

Answer 1

The correct option is A $+8/3D$

For improving near point, convex lens is required and for this convex lens
$u=-25cm,v=-75cm$
$\therefore \frac{1}{f}=\frac{1}{-75}-\frac{1}{-25}\Rightarrow f=\frac{75}{2}cm$
So power $P=\frac{100}{f}=\frac{100}{75/2}=+\frac{8}{3}D$