Q 12-09-202JEE MainJEE Main 2019 (9 Apr, Shift 1)Easy
A concave mirror for face viewing has a focal length of $0.4\ \text{m}$. The distance at which you hold the mirror from your face in order to see your image upright with a magnification of 5 is
Answer: (C) $0.32\ \text{m}$
Upright magnification $m = -\dfrac vu = 5 \Rightarrow v = -5u$. With $f = -0.4\ \text{m}$:
$$\frac1v + \frac1u = \frac{1}{-5u} + \frac1u = \frac{4}{5u} = -\frac{1}{0.4}$$
$$u = -0.32\ \text{m}$$
Hold the mirror $0.32\ \text{m}$ from the face.
Solution by Sreeraj P, M.Sc Physics