$A$ convex lens has power $P$. It is cut into two halves along its principal axis. Further,one piece (out of two halves) is cut into two halves perpendicular to the principal axis as shown in the figure. Choose the incorrect option for the reported lens pieces.

$A$ thin convex lens $L$ (refractive index $= 1.5$) is placed on a plane mirror $M$. When a pin is placed at $A$,such that $OA = 18\, cm$,its real inverted image is formed at $A$ itself,as shown in the figure. When a liquid of refractive index $\mu_l$ is put between the lens and the mirror,the pin has to be moved to $A'$,such that $OA' = 27\, cm$,to get its inverted real image at $A'$ itself. The value of $\mu_l$ will be

Given a thin convex lens (refractive index $\mu_2$),kept in a liquid (refractive index $\mu_1, \mu_1 < \mu_2$) having radii of curvature $|R_1|$ and $|R_2|$. Its second surface is silver-polished. Where should an object be placed on the optic axis so that a real and inverted image is formed at the same place?

An equiconvex lens of focal length $f$ is cut into four equal parts and two parts are placed as shown in the figure. The focal length of the system shown in the figure is:

An equiconvex lens has power $P$. It is cut into two symmetrical halves by a plane containing the principal axis. The power of one part will be

An equiconvex glass lens $(a)$ has a focal length $f$ and power $P$. It is cut into two symmetrical halves $(b)$ by a plane containing the principal axis. The two pieces are recombined as shown in figure $(c)$. The power of the new combination is