Question

A symmetric double convex lens is cut into two equal parts along a plane perpendicular to the principal axis. If the power of the original lens is 4D, the power of the two pieces is :

• A. 2D
• B. 3D
• C. 4D
• D. 5D

Answer 1

The correct option is A 2D

$P_{original}=4D$

$P=P_1+P_2$

$\because$ convex lens is cut into two equal parts

So, $P_1=P_2=P$

$P_{original}=P+P$

$4D=2P$

$P=2D$