Question

A convex lens of focal length f produce virtual image n times the size of the object then the distance of object from the lens is

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

Answer 1

The correct option is C $\left(\frac{n-1}{n}\right)f$

magnification = $n=\frac{v}{u}$

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

Replacing $v=nu$

we get, $u=f\frac{(n-1)}{n}$

Answer. C