Question

An equi-convex lens of focal length ${}^{\prime }{f}^{\prime }$ is cut into two parts along its principal axis, then

• A. refractive index of the lens changes.
• B. radii of curvature of lens changes.
• C. intensity of image formed by each part will reduce to half.
• D. intensity of image formed by each part will becomes twice.

Answer 1

The correct option is C intensity of image formed by each part will reduce to half.

When an equi-convex lens of focal length ${}^{\prime }{f}^{\prime }$ is cut into two parts along its principal axis, then

$1.$ Refractive index $\mu$ of lens does not change.
$2.$ Radii of curvature $R_1$ and $R_2$ of lens will not change.
$3.$ Focal length of each part will be equal to that of initial lens.
$4.$ Intensity of image formed by each part will reduce to half as the number of rays coming out of each part is half of the number that comes out of initial lens.

Hence, option (c) is the correct answer.