An object is placed in front of a concave mirror of focal length 20 cm such that it forms a virtual image which is 4 times the size of the object. The physical distance between the object and the image is

Step-by-step solution

Given, focal length of the concave mirror, f = -20 cm . For a virtual and magnified image, magnification m = +4 . We know that m = - v u 4 = - v u v = -4u . Using the mirror formula: 1 f = 1 v + 1 u 1 -20 = 1 -4u + 1 u - 1 20 = -1 + 4 4u = 3 4u 4u = -60 u = -15 cm . The image distance is v = -4(-15) = +60 cm . Since the object is in front of the mirror and the virtual image is formed behind the mirror, they are on opposite sides of the pole. The physical distance between them is |u| + |v| = 15 + 60 = 75 cm . Answer