Bohr's model cannot explain the emission spectrum of

For a $Bohr$ atom,the angular momentum of an electron is given by $M(n = 1, 2, 3, .....)$ :

What is the radius of the fourth orbit of a hydrogen atom (in $pm$)?

The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom is equal to $\frac{h^{2}}{xma_{0}^{2}}$. The value of $10x$ is ........ . ($a_{0}$ is radius of Bohr's orbit) (Nearest integer) [Given : $\pi=3.14$]

Evaluate the following ratios for the energy of the electron in a particular orbit:
[Kinetic $:$ Potential] and [Total $:$ Kinetic]

The ratio of the minimum wavelengths of the Lyman and Balmer series is ...... .