A thin convex lens of focal length 10 cm and a thin concave... | Physics | SolveeIt | Solveeit

Today, August 18

Question

A thin convex lens of focal length 10 cm and a thin concave lens of focal length 20 cm are in contact. The combination acts as:

A

Concave lens of focal length 10.0 cm

B

Concave lens of focal length 20.0 cm

C

Convex or concave lens depending on refractive index of material of the lens

D

None of the above

Answer

Concave lens of focal length 20.0 cm

Explanation

Solution

$\frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}=\frac{1}{10}-\frac{1}{20},i.,e.F=20\,cm$