Which statement about beam energy is true?

• A. Increasing kVp increases beam energy and penetrability
• B. Increasing kVp reduces beam energy
• C. Increasing mA increases beam energy
• D. Time affects beam energy

Answer: (A)

Beam energy is about the average energy of the photons in the X-ray beam. The kilovoltage peak sets the accelerating potential for the electrons, which directly determines how energetic the produced photons are. When you increase kVp, the energy spectrum shifts to higher energies, so the photons are more penetrating. In other words, higher kVp makes the beam harder and more capable of penetrating tissues. Changing tube current (mA) or exposure time changes how many photons are produced, not how energetic each photon is. So increasing mA or exposure time increases beam quantity, not energy.