A point object moves along the principal axis of a convex lens of focal length f such that its real image, also formed on the principal axis at a distance `(4f)/3` (at t=0) moves away from the lens with uniform velocity `alpha`. Find the velocity of the point object as a function of time t.

Options

A. `((f)/(f+ alpha t))^2 alpha`
B. `((alpha)/(r +alpha t))^2`
C. `((r//3 + alpha t^2)/(f))^2 alpha `
D. `((f)/(f/3 +alpha t ) )^2 alpha`

Answer

D