Q 12-09-060JEE MainJEE Main 2026 (24 Jan, Shift 1)Easy
In a microscope of tube length 10 cm two convex lenses are arranged with focal length of 2 cm and 5 cm . Total magnification obtained with this system for normal adjustment is $(5)^k$. The value of $k$ is ______ .
Answer: (C) 2
Objective $f_o = 2$ cm, eyepiece $f_e = 5$ cm, tube length $L = 10$ cm, $D = 25$ cm. In normal adjustment (final image at infinity):
$$m = \frac{L}{f_o}\cdot\frac{D}{f_e} = \frac{10}{2}\times\frac{25}{5} = 25 = 5^2$$
So $k = 2$.
Solution by Sreeraj P, M.Sc Physics