The radius of the innermost orbit of a hydrogen atom is $5.3 \times 10^{-11} \ m$. The radius of the third allowed orbit of the hydrogen atom is $... \ \mathring{A}$.

The approximate value of the principal quantum number for a circular orbit of a hydrogen atom of radius $530 \ nm$ is

According to Bohr's model, the radius of the second orbit of a helium ion $(He^+)$ is ........ $\mathring{A}$.

$A$ particle of mass $m$ moves in a circular orbit in a central potential field $U(r) = U_{0}r^{4}$. If Bohr's quantization conditions are applied,the radii of possible orbitals $r_{n}$ vary with $n^{1/\alpha}$,where $\alpha$ is ....... .

Explain the quantization of angular momentum by considering the electron as a wave in an atom.

In Bohr's model of the hydrogen atom,the ratio between the period of revolution of an electron in the orbit of $n=1$ to the period of revolution of the electron in the orbit $n=2$ is