When an electron jumps from the $n = 4$ level to the $n = 1$ level,the angular momentum of the electron changes by:

The radius of the electron's second stationary orbit in Bohr's atom is $R$. The radius of the third orbit will be:

The ratio of the radius of the first Bohr orbit to that of the second Bohr orbit of the orbital electron is

For a hydrogen atom,when an electron jumps from $n = 2$ to $n = 1$,the wavelength of the radiation emitted is found to be $\lambda_0$. For which transition of an electron in a $He^+$ ion will the wavelength of the radiation emitted be equal to $\lambda_0$?

In a hypothetical system,a particle of mass $m$ and charge $-3q$ is moving around a very heavy particle having charge $q$. Assuming Bohr's model to be true for this system,the orbital velocity of mass $m$ when it is nearest to the heavy particle is:

Ionization potential of a hydrogen atom is $13.6 \text{ eV}$. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy $12.1 \text{ eV}$. According to Bohr's theory,the number of spectral lines emitted by the hydrogen atoms will be: