Question

if the magnification produced by a concave lens is 1/n+1 then the object distance is​

Answer 1

Explanation:

Concave lenses always produce images that are upright, virtual, reduced in size, and located on the object's side of the lens.

Therefore, the magnification produced by a concave lens is always less than 1.

Answer 2

The distance of the object from the lens is $f(\frac{n}{n+1} )$.

Given:

Magnification of the concave lens $=\frac{1}{n+1}$

To find:

The object distance.

Solution:
The magnification $(M)$ produced by a lens is the ratio of the distance of image produced $(v)$ and the distance of object $(u)$ from the pole of the lens.  

Mathematically,   $M=\frac{v}{u}$

We know, the lens formula as the relation between object distance $(u)$ image distance $(v)$ and focal length $(f)$ of the lens is given by,

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

Multiplying the whole equation by $v$, we get

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

We know, $\frac{v}{u}=M=\frac{1}{n+1}$

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

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

$v=f(\frac{n}{n+1} )$

Final answer:

Hence, the distance of the object from the lens is $f(\frac{n}{n+1} )$.