In an X-ray tube, the accelerating potential between cathode and target is kept fixed. The filament heating is increased so that a larger number of electrons are emitted thermionically from the cathode and reach the target per second. Which change is expected under normal operating conditions?
Options

Question

In an X-ray tube, the accelerating potential between cathode and target is kept fixed. The filament heating is increased so that a larger number of electrons are emitted thermionically from the cathode and reach the target per second. Which change is expected under normal operating conditions?

Options

G1 Physics · Accepted Answer

The filament heating mainly controls thermionic emission from the cathode. Greater emission generally increases the tube current, so more electrons strike the target per second and the X-ray intensity increases. However, the maximum kinetic energy per electron is still determined by the accelerating potential V: K(max) = eV. Therefore the maximum photon energy and the cutoff wavelength remain essentially unchanged when only filament heating is altered. Correct option: C.