A car is fitted with a convex side-view mirror of focal length 20 cm

A car is fitted with a convex side-view mirror of focal length 20 cm. A second car 2.8 m behind the first car is overtaking the first car at a relative speed of 15 m/s. The speed of the image of the second car as seen in the mirror of the first one is

  1. (1/10) m/s
  2. (1/15) m/s
  3. 10 m/s
  4. 15 m/s

Answer

Mirror formula:

(1/v) + (1/-280) = 1/20

(1/v) = (1/20) + (1/280)

v = 280/15

v1 = -(v/u)2 vom

v1 = -(280/15X280)2 . 15

v1 = -15/(15x15)

v1 = -1/15 m/s

The correct option is B.