Question

A converging lens has a focal length of 50 cm. The power of this lens is : (a) + 0.2 D (b) - 2.0 D (c) + 2.0 D (d) - 0.2 D

Answer 1

Convex (So Focal length is positive)

$f=+50cm=+50\times {10}^{-2}m$

$P=\frac{1}{f}=\frac{1}{+50\times {10}^{-2}}=\frac{100}{50}=+2D$