What is the effect of added filtration on the X-ray beam spectrum?

• A. The beam becomes harder and has fewer low-energy photons reaching the patient
• B. The beam becomes softer with more low-energy photons
• C. The beam energy is unaffected
• D. The beam intensity increases with filtration

Answer: (A)

Adding filtration shifts the X-ray spectrum toward higher energies by preferentially absorbing the low-energy photons. Those soft photons contribute less to image quality but more to patient dose, so removing them makes the beam harder and reduces the number of low-energy photons that reach the patient. At the same time, the overall photon fluence drops because some photons are absorbed, so the beam intensity decreases. This combination—higher mean energy with fewer low-energy photons reaching the patient—fits the statement that the beam becomes harder and has fewer low-energy photons reaching the patient.