)2Vo and image will move from focus to infinity (i.e. away from the lens). From the formula, velocity of image
dVi
dt
=
dVi
du
×
du
dt
=2(
f
f+u
)fln(f+u)×5(∵
du
dt
=5m∕s) ⇒
dVi
dt
=10f2
ln(f+u)
f+u
We can see that acceleration of image ∝ ln(𝑓 + 𝑢), i.e varies with distance of object So the image moves away from the lens with a non-uniform acceleration.