A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror, what is the size of image?

Step-by-step solution

Using the relation for the focal length of concave mirror 1 f = 1 v + 1 u ...(1) Differentiating equation (1), we obtain 0=- 1 v^2 d v- 1 u^2 d u So, d v=- v^2 u^2 b (2) (Here : d u=b ) From equation (1) aligned 1 v & = 1 f - 1 u = u-f f u u v & = u-f f aligned v u = f u-f (3) Now, from equations (2) and (3), we get d v=- ( f u-f )^2 b Therefore, size or image is = ( f u-f )^2 b