CBSE Class 11-science Answered

The Rydberg-Ritz Combination Principle is the theory proposed by Walter Ritz in 1908 to explain relationship of the spectral lines for all atoms. The principle states that the spectral lines of any element include frequencies that are either the sum or the difference of the frequencies of two other lines.

An atom can be excited to higher energy either spontaneously or via absorption of a photon. However, according to the principles of Quantum mechanics, these excitations can only occur at certain energy intervals. The Rydberg–Ritz combination principle helps explain this process.

This principle becomes is obvious when we know that spectra are due to transitions between energy levels. An atom can decay from a state 2 to a ground state 0 either directly, or in two steps 2→1 and 1→0. Energy is conserved, E=hf, so the two frequencies (wavenumbers) of the latter route add to the frequency of the first route.

In 1913, Niels Bohr showed this for the hydrogen atom,

We have

Similarly,

Hence