Solving a Mystery: Understanding Scintillation Light

[vertices]

Please look at the file problem.jpg. This is in reference to graph.jpg.

I'm trying to understand the solution (solutions.jpg).

I have a very trivial question. When a gamma ray photons enter the scintillator, it excites a electron, and a small fraction of the excitation energy is given out of visible/UV light during de-exitation. This is scintillation light.

It seems quite useless to me! I mean, what information does the scintillation light give us about the original photon? How on Earth can it give us information about the compton edge (when the energy transferred to the electron is a maximum).

 

[TeethWhitener]

what information does the scintillation light give us about the original photon? How on Earth can it give us information about the compton edge (when the energy transferred to the electron is a maximum)

The incoming high-energy photon will generally induce several events in the defector. The number of events is proportional to the energy of the incoming photon. So the higher in energy the photon is, the higher intensity the light flash of the scintillation will be.