The spectrum obtained from a sodium vapour lamp is an example of

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

Of the following pairs of species,which one will have the same electronic configuration for both members?

The graph between the square root of the frequency of a specific line of characteristic spectrum of $X$-rays and the atomic number of the target will be

The ionisation energy of an electron in the ground state of a helium atom is $24.6 eV$. The energy required to remove both electrons is: (in $eV$)

Pick out the correct statement from the following: