Question

A real object is placed infront of a convex mirror (focal length f). It moves towards the mirror, the image also moves. If $V_i=$ speed of image and $V_0=$ speed of the object and u is the distance of object from mirror along principal axis, then

• A. $V_i<V_0$ if |u| < |f|
• B. $V_i>V_0$ if |u| > |f|
• C. $V_i<V_0$ if |u| > |f|
• D. $V_i=V_0$ if |u| = |f|

Answer 1

Answer: (A), (C)

$V_i<V_0$ if |u| < |f|
$V_i<V_0$ if |u| > |f|

$u=-u$ ;$f=+f$

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$\frac{1}{v}+\frac{-1}{u}=\frac{1}{f}$

$v=\frac{fu}{u+f}$

$\frac{\partial v}{\partial t}=\frac{\partial \frac{fu}{u+f}}{\partial t}$

$v_i=v_o\times \frac{f^2}{(u+f{)}^2}$

$\frac{f}{u+f}<1$

$v_i<v_0$ always

option $A,C$ is correct