The ratio of the velocity of an electron in the second orbit of $He^{+}$ to the third orbit of $B^{4+}$ is:

For a hydrogen atom,the energy of the $n^{th}$ orbit is given by the equation $E \propto n^y$. What is the value of $y$?

The radius of the first excited state of a Helium ion $(He^+)$ is given by (where $a_0$ is the radius of the first stationary state of the hydrogen atom):

What transition in $He^{+}$ ion shall have the same wave number as the first line in Balmer series of hydrogen atom?

The radius of the first Bohr's orbit of the hydrogen atom is ............. $\mathring{A}$.

Which transition in the hydrogen spectrum would have the same wavelength as the Balmer type transition from $n = 4$ to $n = 2$ of $He^+$ spectrum?