Q 12-09-203JEE MainJEE Main 2019 (9 Apr, Shift 2)Easy
A convex lens of focal length $20\ \text{cm}$ produces images of the same magnification 2 when an object is kept at two distances $x_1$ and $x_2$ ($x_1 > x_2$) from the lens. The ratio of $x_1$ and $x_2$ is
Answer: (D) $3:1$
For a lens, $m = \dfrac{f}{f + u}$ with $u$ negative.
Real image ($m = -2$): $-2 = \dfrac{20}{20 + u} \Rightarrow u = -30\ \text{cm}$.
Virtual image ($m = +2$): $2 = \dfrac{20}{20 + u} \Rightarrow u = -10\ \text{cm}$.
$$x_1:x_2 = 30:10 = 3:1$$
Solution by Sreeraj P, M.Sc Physics