From the statements given below :
(A) The angular momentum of an electron in nᵗʰ orbit is an integral multiple of ħ.
(B) Nuclear forces do not obey inverse square law.
(C) Nuclear forces are spin dependent.
(D) Nuclear forces are central and charge independent.
(E) Stability of nucleus is inversely proportional to the value of packing fraction.
Choose the correct answer from the options given below :

Solution

Physics sir · 2 steps

Nuclear forces are charge independent but not central, and that one word knocks out (D).

1. Check each statement. Test each statement on its own against Bohr's model and the properties of nuclear forces. Then pick the option that lists exactly the true ones.

   Statement	True or false	Reason
   (A) L is a multiple of ħ	True	Bohr's quantisation condition: L = mvr = nħ.
   (B) No inverse square law	True	The force is very short range (about 1 to 3 fm). It falls off much faster than 1/r² and is repulsive at very small distances.
   (C) Spin dependent	True	The n–p force is stronger when the two spins are parallel. That is why the deuteron exists only in the parallel-spin state.
   (D) Central and charge independent	False	It is charge independent, but non-central. A tensor part makes it depend on the spin directions, not only on the separation r.
   (E) Stability falls as packing fraction rises	True	Packing fraction = (M - A)/A. A smaller value means more mass went into binding, so the nucleus is more stable.

2. So. The true statements are (A), (B), (C) and (E). That is option (c).

The idea to keep. Nuclear force checklist: strongest, short range, saturating, spin dependent, charge independent and non-central. If a statement calls it central or inverse-square, it is false.

Answer from the NTA final answer key. Solution by PrepWiser.