Question

A thin, symmetric double-convex lens of power P is cut into three parts A,B and C as shown. The power of

• A. $AisP$
• B. $Ais2P$
• C. $Bis\frac{P}{2}$
• D. $Bis\frac{P}{4}$

Answer 1

Answer: (A), (C)

The correct options are
A $AisP$
C $Bis\frac{P}{2}$

Focal length of lens be $f=\frac{1}{P}$
focal length of A is $f$ hence power is $P$ but the focal length of B is $2f$ hence the power of B is $\frac{P}{2}$.