Q 12-09-174JEE MainJEE Main 2020 (8 Jan, Shift 2)Medium
An object is gradually moving away from the focal point of a concave mirror along the axis of the mirror. The graphical representation of the magnitude of linear magnification $(m)$ versus distance of the object from the mirror $(x)$ is correctly given by (graphs are drawn schematically and are not to scale)
Answer: (C) see figure
For a real object beyond $F$ (distance $x > f$) the mirror formula gives
$$|m| = \frac{f}{x - f}$$
Just beyond $x = f$, $|m| \to \infty$.
At $x = 2f$, $|m| = 1$.
As $x$ grows further, $|m|$ keeps decreasing towards $0$.
Only graph (C) starts from a vertical asymptote at $x = f$ and passes through $(2f, 1)$.
Solution by Sreeraj P, M.Sc Physics