In refraction, light waves are bent on passing from one medium to second medium because, in the second medium.

The following figure shows a beam of light converging at point $P$. When a concave lens of focal length $16 \mathrm{cm}$ is introduced in the path of the beam at a place shown by dotted line such that $OP$ becomes the axis of the lens, the beam converges at a distance $x$ from the lens. The value of $x$ will be equal to