The momentum of an electron revolving in the $n^{\text{th}}$ orbit is given by: (Symbols have their usual meanings)

Imagine removing one electron from $He^4$ and $He^3$. Their energy levels,as worked out on the basis of the Bohr model,will be very close. Explain why?

The speed of an electron in the orbit of a hydrogen atom in the ground state is

Imagine that the electron in a hydrogen atom is replaced by a muon $(\mu)$. The mass of the muon particle is $207$ times that of an electron and its charge is equal to the charge of an electron. The ionization potential of this hydrogen atom will be ............. $eV$.

Energy levels $A, B, C$ of a certain atom correspond to increasing values of energy,i.e.,$E_A < E_B < E_C$. If $\lambda_1, \lambda_2, \lambda_3$ are the wavelengths of radiations corresponding to the transitions $C$ to $B$,$B$ to $A$,and $C$ to $A$ respectively,which of the following statements is correct?

What is the change in angular momentum of an electron in a hydrogen atom when it transitions from the $4^{th}$ orbit to the $5^{th}$ orbit? $(h = 6.6 \times 10^{-34} \, J \cdot s)$