Quantum theory was postulated by :

An electron in an atom jumps in such a way that its kinetic energy changes from $x$ to $\frac{x}{4}$. The change in potential energy will be

If the shortest wavelength of $H$ atom in Lyman series is $x$,then the longest wavelength in Balmer series of $He^{+}$ is

The frequency of the first line of the Paschen series in the spectrum of the $Be^{+3}$ ion is:

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?

Find the value of wave number $(\bar{v})$ in terms of Rydberg's constant,when the transition of an electron takes place between two levels of $He^{+}$ ion whose sum is $4$ and difference is $2$.