Question

An equiconvex glass lens $\left(i\right)$ has a focal length $f$ and power $P$. it is cut into symmetrical halves
$\left(ii\right)$ by a plane containing the principle axis. The two pieces are recombined as shown in figure
$\left(iii\right)$ The power of new combination is:

• A. $P$
• B. $P/2$
• C. $2P$
• D. $zero$

Answer 1

The correct option is D $zero$

The net effect of first lens in figure (iii) will be compensated by second lens , So Power of the combination will be zero .

Although if it is asked for the power of only one lens then , there will be no change in power because during cutting lens along principal axis R${}_1$ and R${}_2$ do not change .