Question

If a biconvex lens is cut into identical parts by a horizontal plane xy as shown in the figure, then which of the following statement is correct?

(a) Focal length of each part will be equal and forms image with same intensity. 

(b) Focal length of each part will be same and forms image with reduced intensity. 

(c) Focal length of each part will be different and forms image with reduced intensity. 

(d) None of the above

Answer 1

Answer is (b) Focal length of each part will be same and forms image with reduced intensity.

Since, refractive index μ, radius of curvature R will remains constant, hence focal length will be same.

Since, intensity ∝ (aperture)²

Hence, intensity will be reduced.