Question

A shaving mirror of focal length $f$ produces an image $x$ times the size of the object. If the image is real, then the distance of the object from the mirror is :

• A. $(x+1)f$
• B. $\frac{(x+1)f}{x}$
• C. $\frac{(x-1)f}{x}$
• D. $(x-1)f$

Answer 1

Answer: (B)

$\frac{(x+1)f}{x}$

From mirror equation,

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

Since image is real , magnification$=$$\frac{-v}{u}=-x$

Hence $v=ux$.

Putting this value in first equation gives,

$u=\frac{(x+1)f}{x}$