Question

An equiconvex glass lens has a focal length f and power P. It is cut into two symmetrical halves by a plane containing the principal axis. The two pieces are recombined by keeping side by side. What is the power of new combination.

• A. $P$
• B. $\frac{P}{2}$
• C. $2P$
• D. Zero

Answer 1

The correct option is D

Zero

Each half part has a focal length f. The rays passing through first part will converge downwards while passing through the second part, the rays equally bend upwards. So the power of the combination will be zero.