A bubble in glass slab $\left(\mathrm{\mu }=1.5\right)$ when viewed from one side appears at $5\mathrm{cm}$ and $2\mathrm{cm}$ from other side, then thickness of slab is

An equiconvex lens is cut into two halves along (i) ${\mathrm{XOX}}^{\text{'}}$ and (ii) ${\mathrm{YOY}}^{\text{'}}$ as shown in the figure. Let $\mathrm{f},{\mathrm{f}}^{\text{'}},{\mathrm{f}}^{"}$ be the focal lengths of the complete lens of each half in case (i), and each half in case (ii), respectively. Choose the correct statement from the following

A point object is moving with speed $u_0$ at a position somewhere between $2F$ and $F$ in front of a convex lens. The speed of its image is