What is the experimental evidence in support of the idea that electronic energies in an atom are quantized ?

Explanation

The line spectrum of any element has lines corresponding to definite wavelengths. Lines are obtained as a result of electronic transitions The w avelength is distance betw een two successive peaks or two successive troughs of a wave. So, X = 4 x 2.16 pm = 8.64 pm 37 between the energy levels. So, the electrons in these levels have fixed energy, i.e., quantized values.