X-ray production
An electron with some kinetic energy emits photons as it hits an object. Classically, we would expect the electron deceleration to emit an electromagnetic wave. Since the deceleration is random, we expect a continuous spectrum of photon wavelengths.
However, we see there is a minimum wavelength below which no photons appear.
This minimum wavelength corresponds to the case where all the electron energy is emitted as a single photon with energy .
Note
There are spikes (omitted for clarity) in the intensity at the dashed lines due to electrons falling to lower energy levels as described by the Bohr model.
The classical model is shown:
