Question

A convex lens has power \( P \). It is cut into two halves along its principal axis. Further, one piece (out of two halves) is cut into two halves perpendicular to the principal axis as shown in the figure. Choose the incorrect option for the reported lens pieces. 

• A. Power of \( L_1 \) is \( P \)
• B. Power of \( L_1 \) is \( \frac{P}{2} \)
• C. Power of \( L_2 \) is \( \frac{P}{2} \)
• D. Power of \( L_2 \) is \( P \)

Hint:

When a lens is cut along its axis, the power of each piece is halved.

Answer 1

The Correct Option is D

- A convex lens has power \( P \). When the lens is cut into two halves along its principal axis, the focal length of the two pieces remains the same, but the power of each piece becomes half of the original power. - Hence, the power of \( L_1 \), which is one of the two halves, will be \( \frac{P}{2} \). - The second piece \( L_2 \), which is cut into two halves perpendicular to the principal axis, will also have the same power \( \frac{P}{2} \). Therefore, the incorrect option is (4): Power of \( L_2 \) is \( P \).