Which sequence correctly describes the basic process of x-ray production in an x-ray tube?

• A. Emission of x-ray photons from the filament
• B. Emission of electrons from the filament, accelerated by high voltage, and decelerated in the target to produce x-rays
• C. Nuclear fusion in the target
• D. Thermal conduction heating

Answer: (B)

The basic process starts with electrons being released from the heated filament (thermionic emission). These electrons are then accelerated toward the target by the high voltage across the tube, gaining kinetic energy as they speed up. When they strike the target, they slow down rapidly in the nuclear field of the atoms, producing x-ray photons in the process (bremsstrahlung). Some collisions also eject inner-shell electrons, and when another electron fills those vacancies, characteristic x-rays are emitted at specific energies. This sequence—emission of electrons from the filament, acceleration by high voltage, and deceleration in the target to produce x-rays—best describes how x-rays are produced in an x-ray tube. X-rays aren’t emitted from the filament, nuclear fusion isn’t involved, and thermal conduction heating alone doesn’t generate x-rays.