Two $\alpha$ particles having speeds $\mathrm{S}_{1}$ and $\mathrm{S}_{2}$ have kinetic 1 and 2 MeV respectively; the relationship between $\mathrm{S}_{1}$ and $\mathrm{S}_{2}$ is
(a)$\mathrm{S}_{1}=2 \mathrm{S}_{2}$
(b)$\mathrm{S}_{2}=2 \mathrm{S}_{1}$
(c)$\mathrm{S}_{2}=\sqrt{2 \mathrm{S}_{1}}$
(d)$\mathrm{S}_{1}=\sqrt{2 \mathrm{S}_{2}}$
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed C; on checking, D is correct — see the explanation.
Printed C; ¹S is allowed, ³D is the forbidden term.
Explanation
np² (equivalent electrons) allows only ¹S, ³P and ¹D (Pauli); ³D would need two electrons with the same m_l and the same spin, so it is not allowed.