Question

A convex mirror of focal length f produces an image (1/n) th of the size of the object. The distance of the object from the mirror is

• A. nf
• B. f/n
• C. (n + 1)f
• D. (n - 1)f

Answer 1

The correct option is C (n + 1)f

As the image formed by a convex mirror is always virtual and erect, so

u = -ve,
v = +ve, f = +ve
In magnitude, $m=-\left(v/u\right)=+\left(1/n\right)orv=-\frac{u}{n}$

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

$or\frac{(n+1)}{u}=-\frac{1}{f}oru=-(n+1)f$
i.e., object is in front of mirror at a distance (n + 1) f. Hence, the correct answer is option (c).