Two nuclei of mass number 3 combine with another nucleus of mass number 4 to yield a nucleus of mass number 10. If the binding energy per nucleon for the mass numbers 3,4 and 10 are $5.6 \mathrm{MeV}, 7.4 \mathrm{MeV}$ and 6.1 MeV , respectively, then in the process, $\Delta \mathrm{Mc}^2=$ $\_\_\_\_$ MeV .

The binding energy per nucleon of $^{209}_{83}Bi$ is _______ MeV.

[Take $m(^{209}_{83}Bi) = 208.980388\ \text{u}$, $m_p = 1.007825\ \text{u}$, $m_n = 1.008665\ \text{u}$, $1\ \text{u} = 931\ \text{MeV}/c^2$]

Angular momentum of an electron in a hydrogen atom is $\frac{3h}{\pi}$, then the energy of the electron is _____ eV.

A nucleus has mass number $\alpha$ and radius $R_{\alpha}$. Another nucleus has mass number $\beta$ and radius $R_{\beta}$.

If $\beta = 8\alpha$ then $R_{\alpha} / R_{\beta}$ is :