Q196 / 200 · Manipal (MET) 2013 · Physics

The ratio of the speed of an object to the speed of its real image of magnification $m$ of a convex mirror is

  • Correct answer
    A
    $-\frac{1}{m^2}$
  • B
    $m^2$
  • C
    $-m$
  • D
    $\frac{1}{m}$

Solution

$\frac{1}{u}+\frac{1}{v}=\frac{1}{f}$ $\begin{aligned} & -\frac{1}{u^2} \frac{d u}{d t}-\frac{1}{v^2} \frac{d v}{d t}=0 \\ & =-\frac{1}{u^2} u_0-\frac{1}{v^2} v_0=0 \\ \frac{u_0}{v_0} & =-\frac{u^2}{v^2}=-\frac{1}{m^2}\end{aligned}$

Hence, the correct answer is option: 'A'.

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