Removing filtration from an x-ray beam would result in the spectrum becoming:

• A. Softer spectrum
• B. Harder spectrum
• C. No change
• D. More monochromatic

Answer: (A)

Filtration shapes the energy distribution of the x-ray beam by absorbing more of the low-energy photons than the high-energy ones. When filtration is in place, it trims off many of the low-energy photons, which raises the average energy of the transmitted beam, producing a harder spectrum. Removing filtration reverses this effect: more low-energy photons survive, lowering the average energy and yielding a softer spectrum. A harder spectrum would result from adding filtration, not removing it. The spectrum would not become monochromatic simply by removing filtration; it remains polyenergetic, albeit with a lower average energy.