Find the distance of an object from a convex lens if image is
two times magnified. Focal length of the lens is `10cm`

Explanation

Convex lens forms both type of images real as well as virtual. Since, nature of the image is not mentioned in the question, we will have to consider both the cases.
When image is real Means v is positive and u is negative with `absv=2absu`. Thus if
u=-x then, v=2x and f=10 cm
Substituting in ,`1/v-1/u=1/f`
we have, `1/(2x)+1/x=1/10or3/(2x)=1/10`
`therefore x=15 cm`
x=15 cm , means object lies between F and 2F.
When image is virtual Means v and u both are negative. So let
u=-y then v=-2y and f=10 cm
Substituting in,`1/v-1/u=1/f`
we have, `1/(-2y)+1/y=1/10or1/(2y)=1/10`
`therefore` y=5 cm
y=5 cm, means object lies between F and P.