A point object is moving uniformly towards the pole of a concave mirror of focal length 25cm along its axis as shown below. The speed of the object is 1 ms. At t= 0, the distance of the object from the mirror is 50cm. the average velocity of the image formed by the mirror between time t = 0 and t = 0.25 s is:

Options

A. Zero
B. 40 cm `s^(-1)`
C. Infinity
D. 20 cm `s^(-1)`

Answer

C

Explanation

(c): At t = 0, u = 50 cm (Placed at 2f), v = 50 cm After 25 s, u = 50 – 25 = 25 cm (object is at f), v=infinity
So, velocity of image = `("infinity" -50)/(25)` = infinity