I'm trying to solve the following problem for a course in radiation physics.

A thin ray of intensity $I_0$ and energy $E_0$ impacts in a material. What is the intensity and the energy of the photons after having travelled a distance d?

I know that the intensity decreases as a negative exponential, but I was wondering how to calculate the change in the energy.

The only process relevant for this I think that must be incoherent scattering (because in both pair production and photoelectric effect the photon is absorbed) so I thought about calculating the energy transferred by the photons and subtracting it from the initial energy.

I also thought about calculating the energy transfer coefficient but I think that I lack information to do it this way.

How can I calculate the energy after having travelled a distance d?


Typically, this sort of problem is solved by an MCNP simulation

If you assume that all the photons that collide with an atom are absorbed, then the energy is jsut E_0.

With charged particles, there is the phenomenon of energy strangling.

other then that, I can think of the following: You might be able to some how average the compton-scattering equation to get some sort of mean energy for photons that undergo compton scattering, but you'd need to know material information. There's also the klien-neshina formula that you might be able to parameterize your answer in terms of.

  • $\begingroup$ Looking at this question again, your professor probably wants the answer "The intensity is reduced by a factor mu*dx and the energy stays the same." It's a trivial answer but correct to a first order. $\endgroup$ – Terry Price Jul 9 '18 at 17:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.