Question

Power of a biconvex lens is \( P \) diopter. When it is cut into two symmetrical halves by a plane containing the principal axis, the ratio of the power of two halves is:

• A. 1:2
• B. 2:1
• C. 1:4
• D. 1:1

Hint:

When a lens is cut along the principal axis, its focal length remains unchanged, and hence its power remains the same.

Answer 1

The Correct Option is D

Step 1: {Understanding Lens Power}
The power of a lens is defined as the reciprocal of its focal length: \[ P = \frac{1}{f} \].
Step 2: {Consequences of Bisecting a Lens Along the Principal Axis}
When a symmetrical biconvex lens is divided into two equal parts along its principal axis, the focal length of each resultant part is identical to that of the original lens.
As lens power is inversely proportional to focal length, the power of each half remains constant.
Consequently, the ratio of power between the two halves is: \[ 1:1 \]. The correct answer is therefore \( 1:1 \).