Final answer:
In high harmonic generation, the intensity of the emitted light drops, then stays constant, and then drops again when the frequency of the original beam is increased. This is because the energy of the photons and the threshold frequency for ejecting electrons play a role in determining the intensity of the emitted light.
Step-by-step explanation:
In high harmonic generation, the intensity of the emitted light initially drops, then stays constant, and finally drops again when the frequency of the original beam is increased. This phenomenon can be explained by the relationship between the energy of the photons and the threshold frequency for ejecting electrons.
When the frequency of the original beam is increased, the energy of the photons also increases. Initially, as the frequency increases, the energy of the photons becomes sufficient to eject electrons, and thus the intensity of the emitted light drops. However, as the frequency further increases, the energy of the photons becomes too high for the electrons to be ejected, resulting in a constant intensity of the emitted light. Finally, when the frequency becomes even higher, the number of photons created at that frequency becomes too few for the energy intensity to continue to increase, causing another drop in intensity.