Question

Mention the two features of x-ray spectra, not explained by classical electromagnetic theory.

Answer 1

Though classical electromagnetic theory suggests the emission of radiations from accelerating electrons, it could not explain two features exhibited by x-ray spectra. These features are given below

1. For a given accelerating voltage, the lower limit for the wavelength of continuous x-ray spectra is the same for all targets. This minimum wavelength is called cut-off wavelength.
2. The intensity of x-rays is significantly increased at certain well-defined wavelengths as shown in the case of characteristic x-ray spectra for molybdenum.