The maximum energy of bremsstrahlung photons is controlled by which technical factor?

• A. tube current
• B. exposure time
• C. source-to-image distance
• D. tube potential

Answer: (D)

In X-ray production, the highest-energy photons come from electrons that are accelerated across the tube potential before they interact in the target. The tube potential sets how much kinetic energy each electron gains, and when those electrons are decelerated, photons can be emitted with energies up to that initial electron energy. So increasing the tube potential raises the maximum possible photon energy and shifts the spectrum to higher energies.

Tube current and exposure time mainly affect how many photons are produced, not how energetic they can be. Source-to-image distance changes beam intensity and geometric factors but does not set the maximum photon energy.