Question

A narrow beam of 200 keV photons is normally incident on a 1.4 cm thick sheet of aluminum pressed against a 2 mm thick sheet of lead. What fraction of the incident photons penetrates both sheets without interacting? If the layers were switched, would there be a difference? Why or why not?

Answer 1

from above calculated equations , it shows that it does not make a difference if you place the aluminium first or lead first. As the total thickness of sheets remains the same.