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, we get
`:. (-1)/(v^(2))(d v)/(d t) - (1)/(u^(2))(d u)/(u^(2)) = 0`
or `(d u//dt)/(d v//dt) = -(u^(2))/(v^(2)) = -(1)/(m^(2))` `(because m = (v)/(u))`