An object placed on the principle axis of a convex lens of focal length 10m produces a real image of double magnification. The image distance from the lens is
A. 30cm B. 25cm C. 20cm D. 15cm E. 10cm
Correct Answer: A
Explanation
\(\frac{1}{v}\) + \(\frac{1}{u}\) = \(\frac{1}{f}\) \(\frac{1}{v}\) = +ve real image distance where; U = +ve real object distance f = real focus = 10 m = magnification M = 2 = \(\frac{v}{u}\) 2u = V \(\frac{1}{2u}\) + \(\frac{1}{u}\) = \(\frac{1}{10}\) 2u = 30 u = 15cm v = 2u = 2 x 15 = 30cm
