In Bohr's model,if the atomic radius of the first orbit is ${r_0}$,then the radius of the fourth orbit is

Suppose in a hypothetical world,the angular momentum is quantized to be even integral multiples of $\frac{h}{2 \pi}$. According to Bohr's model,what will be the largest possible wavelength emitted by hydrogen atoms in the visible range in this world (in $text{ nm}$)? (Consider $hc = 1242 \text{ eV-nm}$)

$A$ hydrogen atom at rest emits a photon during its transition from $n = 2$ to $n = 1$. Choose the $INCORRECT$ statement.

The radius of the smallest electron orbit in a hydrogen-like ion is $(0.51/4 \times 10^{-10}) \text{ m}$. This ion is:

The magnitude of acceleration of the electron in the $n$th orbit of a hydrogen atom is $a_{H}$ and that of a singly ionised helium atom is $a_{He}$. The ratio of $a_{H} : a_{He}$ is

Consider a hydrogen-like atom whose energy in the $n^{th}$ excited state is given by $E_n = - \frac{13.6 Z^2}{n^2}$. When this excited atom makes a transition from an excited state to the ground state, the most energetic photons have energy $E_{max} = 52.224 \ eV$ and the least energetic photons have energy $E_{min} = 1.224 \ eV$. The atomic number of the atom is: