Question

The power of a double convex lens of radius of curvature $R$ each is $Y$. The power of a plano convex lens of same material and of radius of curvature $2R$ is

• A. $\frac{Y}{4}$
• B. $\frac{Y}{2}$
• C. $2Y$
• D. $4Y$

Answer 1

Answer: (A)

$\frac{Y}{4}$

Using the lens maker's formula:
$p=(\mu -1)\left(\frac{2}{R}\right)$

Thus, the ratio of the 2 powers will be:
$\frac{p_1}{p_2}=\frac{\frac{2}{R}}{\frac{1}{2R}}$

Thus, $p_2=\frac{p_1}{4}$