Increasing kVp reduces the difference between minimum and maximum photon energies.

• A. Increases the difference
• B. No change
• C. Reduces the difference between min and max photon energies
• D. Not defined

Answer: (C)

The key idea is that an x-ray beam from a tube has a continuous spectrum that extends from near zero energy up to a maximum energy equal to the tube potential (kVp). The minimum energy is effectively determined by filtration and inherent absorption, but the maximum energy clearly increases as kVp increases.

When you raise kVp, the highest-energy photons become more energetic, so the range of photon energies in the beam broadens. In other words, the difference between the smallest and largest photon energies grows because the upper end moves upward while the lower end stays roughly the same (unless you change filtration). Therefore, increasing kVp increases, not decreases, the spread of photon energies. The statement that it reduces the difference contradicts this tend, so the correct understanding is that the energy range widens with higher kVp.