Two lenses of power (-15, D) and (+ 5,D) are in contact with... | Physics | SolveeIt | Solveeit

Today, August 20

Question

Two lenses of power $-15\, D$ and $+ 5\,D$ are in contact with each other. The focal length of the combination is

A

$-20\, cm$

B

$-10\, cm$

C

$+20\, cm$

D

$+10\, cm$

Answer

$-10\, cm$

Explanation

Solution

$P=P_{1}+P_{2}=-10$ $t=\frac{1}{P} \Rightarrow 0.1\,m \Rightarrow -10\,cm$