1.
(a) What determines the highest energy of x-ray photons emitted from an x-ray tube?
Tube voltage
(b) In x-ray imaging for medical applications, why are low-energy photons undesired? What measures can be taken to reduce the number of low-energy photons entering the human body?
Low energy photons are absorbed by tissue and thus potentially harmful while not at all useful for imaging applications.
We can limit the number of low energy photons by using filters (e.g. such as thin aluminum plates) that screen the low energy photons while allowing higher energy photons to be transmitted.
(c ) why are photons undergoing scattering undesired? What measures can be taken to prevent these photons form entering the detectors?
Scattered photons, created normally by Compton scattering, appear as noise in an x-ray image since their direction is random. We can prevent (or at least reduce them) by using grids in front of the detectors.

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