In a hydrogen atom,an electron makes a transition from the $n=4$ to the $n=1$ energy level. The recoil momentum of the $H$ atom will be:

An electron is moving in an orbit of a hydrogen atom from which there can be a maximum of six transitions. An electron is moving in an orbit of another hydrogen atom from which there can be a maximum of three transitions. The ratio of the velocities of the electron in these two orbits is

In the lowest energy level of a hydrogen atom,the electron has an angular momentum of:

The radius of the first permitted Bohr orbit for the electron in a hydrogen atom equals $0.53 \mathring{A}$ and its ground state energy equals $-13.6 \; eV$. If the electron in the hydrogen atom is replaced by a muon $(\mu^{-})$ [charge same as electron and mass $207 m_{e}$], the first Bohr radius and ground state energy will be:

Energy required for the electron excitation in $Li^{++}$ from the first to the third Bohr orbit is.....$eV$

An electron in a hydrogen atom undergoes a transition from a higher energy level to a lower energy level. The incorrect statement of the following is