Which statement best describes what happens to the beam when filtration is properly applied?

• A. The beam becomes more polychromatic
• B. The beam becomes less polychromatic and more monochromatic
• C. The beam energy becomes more variable
• D. The beam intensity increases without changing quality

Answer: (C)

Filtration removes the low-energy photons from the x-ray beam. Those soft photons contribute to patient dose but not to image quality, so taking them out hardens the beam. A harder beam has a higher average energy and a spectrum that is narrower in energy content, meaning the beam is less polychromatic and closer to monoenergetic. So the correct idea is that proper filtration reduces energy spread and improves beam quality, not that the energy becomes more variable. (Filtration generally decreases overall intensity unless exposure factors are increased to compensate.)