Which statement describes the function of the aluminium filter in simple terms?

• A. To cool the X-ray tube
• B. To increase beam intensity
• C. To remove low energy photons
• D. To shape the beam

Answer: (C)

The idea here is that the aluminium filter reduces the amount of low-energy photons in the X-ray beam. Those soft photons don’t penetrate tissues well and just add dose without helping create a better image. By removing them, the beam becomes harder (higher average photon energy), which lowers patient dose and can improve image contrast. The filter doesn’t cool the X-ray tube, and it doesn’t increase beam intensity—some photons are absorbed, so exposure may need to be adjusted. It also doesn’t shape the beam; that’s the job of collimation.