Q. A lens of power $+ 2\ dioptres\ $is placed in contact with a lens of power $- 1\ dioptre$. The combination will behave like
A) A divergent lens of focal length $50\ cm$
B) A convergent lens of focal length 50 $cm$
C) A convergent lens of focal length 100 $cm$
D) A divergent lens of focal length 100 $cm$
Explanation
(c) $P = P_{1} + P_{2} \Rightarrow P = + 2 + ( - 1) = + 1D$
$f = \frac{+ 100}{P} = \frac{+ 100}{1} = 100\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.