Question

Convex lens of focal length 15 cm is kept in front of concave lens of focal length 30 cm. Find the power of system of lens.

• A. - 0.033 D
• B. + 0.033 D
• C. - 0.6 D
• D. + 0.6 D

Answer 1

The correct option is B

+ 0.033 D

($P_{total}$) = $P_{|}$ + $P_{||}$

= $\frac{1}{f_1}$ + $\frac{1}{f_2}$

= $\frac{1}{15}$ - $\frac{1}{30}$ (concave lens, so $f_2$ = - 30)

$P_{total}$ = + 0.33 D