A particle moves towards a concave mirror of focal length `30cm` along its axis and with a constant speed of `4cm//sec`. At the instant the particle is `90cm` from the pole

Options

A. velocity of image is `1 cm//sec`
B. velocity of image w.r.t. particle is `5cm//sec`
C. particle and image move towards each other
D. as the particle approaches pole, velocity of image increases

Explanation

`(1)/(v)+(1)/(-90)=(1)/(-30)`
`rArr (1)/(v)=(1)/(90)+(1)/(30)=(1-3)/(90)= -(2)/(90)rArrv= -45cm`
`(dv)/(dt)= -(v^(2))/(u^(2))(du)/(dt)= -(45^(2))/(90^(2))xx4= -1m//s`