Question

A man's near point is $0.5 \, m$ and far point is $3 \, m$ . Power of spectacle lenses required for

(i) reading purposes

(ii) seeing distant objects, respectively are

• A. $-2 \, $ $D$ and $+3D$
• B. $+2 \, $ $D$ and $-3D$
• C. $+2 \, $ $D$ and $-0.33D$
• D. $-2 \, $ $D$ and $+0.33D$

Answer 1

Answer: (C)

For reading purpose
$u=-25 \, cm,v=-50 \, cm, \, f=?$
$\therefore \frac{1}{f}=\frac{1}{v}-\frac{1}{u}=\frac{1}{50}+\frac{1}{25}=\frac{1}{50}$
$P=\frac{100}{f}=+2D$
For distinct vision,
$f^{′}=$ distance of far point $ \, =-3$ $m$
$P \, $ = $ \, \frac{1}{f ′}=-\frac{1}{3}$ $D$ = $-$ $0.33D$