The main function of cadmium used in the nuclear reactor is:

What is the frequency of the electron in the first orbit of hydrogen atom of orbital radius $0.5 \times 10^{-10} \mathrm{~m}$, if its orbital velocity in that orbit is $2.2 \times 10^6 \mathrm{~ms}^{-1}$.

If the ratio of the nuclear radii of two atoms is $2: 3$ then the ratio of their mass numbers is:

The atomic mass of an element $10 X^{20}$ is 19.98170 amu. The binding energy per nucleon of that element is: [given mass of neutron = 1.00867amu and mass of proton = 1.00783 amu and 1amu = 931 MeV ]