If the binding energy per nucleon of deuteron $\left({ }_1 \mathrm{H}^2\right)$ is 1.15 MeV and an $\alpha$-particle has a binding energy of 7.1 MeV per nucleon, then the energy released per nucleon in the given reaction is

$$ { }_1 \mathrm{H}^2+{ }_1 \mathrm{H}^2 \rightarrow{ }_2 \mathrm{He}^4+\mathrm{Q} $$

The ratio of the time periods of the revolution of the electrons in the second and third excited states of hydrogen atom is

If the surface areas of two nucleii are in the ratio $9: 47$, then the ratio of their mass number is

The ratio of energies of photons produced due to transition of an electron in hydrogen atom from second energy level to first energy level and fifth energy level to second energy level is