The orbital angular momentum of an electron in $d$-orbital is equal to

In hydrogen atom, the minimum energy required to excite an electron from 2nd orbit to the 3rd orbit is

The velocity $(v)$ of de-Broglie wave is given by

$$ \left[\begin{array}{l} v=\text { frequency } \\ m=\text { mass } \\ C=\text { velocity } \text { of } \text { light } \end{array}\right] $$

Given the ratio of kinetic energy of electron in two orbitals is $16: 9$. Calculate the ratio of wavelength of electron waves?