Final answer:
The two factors that control differences in x-ray intensity across the focal spot are the type of radiation, which affects penetration into matter, and the energy of individual photons, influencing both penetration and imaging contrast.
Step-by-step explanation:
The differences in x-ray intensity across the focal spot are controlled mainly by two factors which are:
- The type of radiation, which dictates how far it can penetrate into matter. Different types of radiation penetrate materials to different extents. For example, alpha particles have a short penetrating distance due to their high charge and mass, quickly interacting with material and losing energy.
- The energy of the individual photons. Higher energy photons can penetrate deeper into materials before being absorbed or scattered, whereas lower energy photons tend to be absorbed more easily, providing better contrast for imaging but having less penetration power.
These factors are critical in medical imaging and materials analysis to optimize the x-ray imaging process and ensure the best possible contrast and resolution within safety limits.