The correct option is
B The induced charges appearing on
S1 are uniformly distributed.
Electric field inside a cavity in a conductor is always zero. Even if the conductor is charged or charges are induced on a neutral conductor by an external field, all charges reside only on the outer surface of the conductor. Hence, any cavity of any shape and size is always shielded from outer electric influence.
So, the electric field due to
S1 and
Q at point
P is zero, due to electrostatic shielding.
Due to the induction process, the
+Q charge placed at centre induces
−Q charge on the surface
S1. Since the surface area of
S1 is uniform and the charge is placed at the centre of the cavity, so the induced charge will be uniformly distributed.
Since the conductor is electrically neutral,
+Q charge appears on
S2. The surface is non-uniform so, the induced charge on it will be non-uniformly distributed (charge density inversely proportional to radius of curvature).
Hence, option (a) and (b) are correct statements.