Question

If lens A has focal length $+15cm$ and lens B has focal length $+30cm$, find out which lens has more power?

• A. Lens A has more power
• B. Lens B has more power
• C. Power of the lens cannot be determined
• D. Both have the same power

Answer 1

The correct option is A

Lens A has more power

Given:
Focal length of lens A, $f_A=+15cm=+0.15m$
Focal length of lens B, $f_B=+30cm=+0.30m$

Power of lens is given by:
$P=\frac{1}{\text{Focal length}}$

Hence,
Power of lens A:
$P_A=\frac{1}{0.15}=6.66D$

Power of lens B:
$P_B=\frac{1}{0.30}=3.33D$

$⟹P_A>P_B$