A thin converging lens is placed between an object and a screen whose the sharp image of the object is formed on the screen. Find the transverse diamension of the object if at one position of the lens the image diamension equals `h' = 2.0 mm` and at the other, `h'' = 4.5 mm`.

Explanation

We know from the prevous problem that the two magnifications are reciprocals of each other `(beta' beta'' = 1)`. If `h` is the size of the object then `h' = beta' h` and
`h'' = beta'' h`
Hence `h = sqrt(h' h'')`.