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 figure. Choose the incorrect option for the reported lens pieces

The image formed by an objective lens of a compound microscope is

If $r$ and $r^1$ denotes the angles inside the prism having angle of prism $50^{\circ}$ considering that during interval of time from $t=0$ to $t=t, r$ varies with time as $r=10^{\circ}+t^2$. During the time $r^1$ will vary with time as

In determining the refractive index of a glass slab using a travelling microscope, the following readings are tabulated

(a) Reading of travelling microscope for ink mark $=5.123 \mathrm{~cm}$

(b) Reading of travelling microscope for ink mark through glass slab $=6.123 \mathrm{~cm}$

(c) Reading of travelling microscope for chalk dust on glass slab $=8.123 \mathrm{~cm}$

From the data, the refractive index of a glass slab is