Hydrogen atom:
The electronic ground state of hydrogen atom contains one electron in the first orbit. If sufficient energy is provided, this electron can be promoted to higher energy levels. The electronic energy of a hydrogen-like species (any atom//ions with nuclear charge Z and one electron) can be given as
`E_(n)=-(R_(H)Z^(2))/(n^(2))` where `R_(H)= "Rydberg constant," n= "principal quantum number"`
Calculate the wavelength of light (nm) for the electronic transition of H-atom from the first excited state to ground state.
In the model of hydrogen like atom put forward by Niels Bohr `(1913)` the electron orbits around the central nucleus. the bohr radius of `n^(th)` orbit of a hydrogen-like species is given by
`r= k n^(2)/Z` " " where, k is constant

Answer

`121.9 nm`