Question

A real image of transverse magnification n is formed
by a concave mirror of focal length. F. Shows what
the object is placed at a distance of (n+1) f/n from
the mirror.
​

Answer 1

Explanation:

So given that the image is 1/n the object size, then proportionately the image distance di is also 1/n the object distance do:

di = do/n.

If you substitute [do/n ] for di in the lens equation, then 1/di + 1/do = 1/f becomes:

n/do + 1/do = 1/f ,

then (n +1) /do = 1/f.

So finally,

do = f(n +1).

EDIT: BTW, you can also we can find the image distance by dividing this value by n:

di = f(n +1)/n.