A concave mirror produces magnification of 1/2 when an object is placed at a distance of 50 cm from it. Where should the object be placed so that the virtul image of double the size is formed by the mirror?

Ans: 10cm.

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Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

magnification = v/u = 1/2 = -(h₁/h)

         v/-50 = 1/2

          v =-25cm

 1/v + 1/u = 1/f

 -1/25 + -1/50 = 1/f

     f = -50/3       (focal length)

let it is placed at u distance from mirror then

  v/u = h¹/h = 2             (given)

 v = 2u

applying mirror formula

1/v + 1/u = 1/f

 1/2u + 1/u = 1/f

 3/2u = 1/f

  u = 3f/2

 u = -25cm

thus object should be placed at 25cm from mirror