Question

how far should an object be from a converging mirror of radius 36cm to form a real image one - ninth of its size​

Answer 1

focal length :

`{ \tt{f = (r)/(2) }} \\ focal \: length = (36)/(2) = 18 \: cm`

From linear magnification:

`{ \tt{ (1)/(m) + 1 = (u)/(f) }} \\ (1)/(9) + 1 = (u)/(18) \\ \\ u = (18 * 10)/(9) \\ u = 20 \: cm`

The object must be at 20 cm