Bohr’s model of atom explains :

The emission spectrum of hydrogen discovered first and the region of the electromagnetic spectrum in which it belongs,respectively,are

In the Bohr model of an atom,the radius of a hydrogen atom in the ground state is $r_1$ and the radius of a $He^{+}$ ion in the ground state is $r_2$. Which of the following is correct?

If the binding energy of electrons in a metal is $250 \ kJ \ mol^{-1}$,what should be the threshold frequency of the striking photons in order to free an electron from the metal surface?

Which of the following is correct for the Humphrey series of the hydrogen spectrum?

The kinetic energy of an electron is $5.65 \times 10^{-25} \ J$. Find the frequency of the electron.