The third line in the Balmer series corresponds to an electronic transition between which Bohr's orbits in hydrogen?

If the longest wavelength of the spectral line of the Paschen series of $Li^{2+}$ ion spectrum is $x \ \mathring{A}$,then the longest wavelength (in $\mathring{A}$) of the Lyman series of the hydrogen spectrum is

Which one of the following is not the characteristic of Planck's quantum theory of radiation?

The difference in wavelength of first and second spectral lines of Lyman series in $Li^{2+}$ ion spectrum is ................ $\mathring{A}$

In an orbital,the value of $K.E.$ is equal to:

In an electron transition from an infinite state to the ground state in an $H$ atom,find the emitted wavelength. (in $nm$)