Question

The ratio of the speed of an object to the speed of its real image of magnification `m` in the case of a convex mirror is.
A. `- (1)/(m^2)`
B. `m^2`
C. `- m`
D. `(1)/(m)`

Answer 1

Correct Answer - A
As `(1)/(v)+(1)/(u)=(1)/(f)`
Differentiating w.r.t.t, we get
`:. (-1)/(v^2) (d v)/(dt)-(1)/(u^2) (du)/(dt) = 0`
or `(du//dt)/(dv//dt) = - (u^2)/(v^2) = -(1)/(m^2)` `(because m = (v)/(u))`.