Question

An equiconvex lens is made from glass of refractive index $1.5$. If the radius of each surface is changed from $5cm$ to $6cm$, then the power:

• A. Remains unchanged
• B. Increases by $3.33D$
• C. Decreases by $3.33D$
• D. Decreases by $5.5D$

Answer 1

Answer: (C)

Decreases by $3.33D$

initial power be $D$
$f=R=5$
$D=\frac{1}{f}=\frac{1}{5}=0.2$
final power is $\frac{1}{6}=0.17$
power is decreased by $3.33D$
option $C$ is correct