In a displacement method using lens, we obtain two images for separation of the lens d. One image is magnified as much as the other is diminshed . If m is the magnification of one image, find the focal length of the lens.

Explanation

From above question `f= (d )/( m_(1) - m_(2))` here if `m_(1) ` is taken as `m, m_(2) = (1)/(m ) ` so f becomes `(m d)/( (m^(2) - 1))`