Question

In a Coolidge tube
A) The intensity of x-rays is controlled by filament current
B) The intensity of x-rays is controlled by the accelerating voltage.
C) As the accelerating voltage is increased ${\lambda }_{min}$ is decreased
D) ${\lambda }_{min}$ is controlled by filament current

• A. a, c
• B. b, d
• C. b, c
• D. a, d

Answer 1

The correct option is A a, c

In the Coolidge tube, the electrons are produced by thermionic effect from a tungsten filament heated by an electric current. The filament is the cathode of the tube.
The high voltage potential is between the cathode and the anode, the electrons are thus accelerated, and then hit the anode. So the intensity of X-rays is controlled by filament current. And in this process the incoming electrons transfer their energy to the X-rays that are then emitted from the sample. The maximum energy (or the minimum wavelength) X-rays are produced when all the energy is transferred. This is the short wavelength limit (SWL) of the continuous X-rays. The wavelength is related to the applied voltage by the following relation:
$eV=\frac{hc}{\lambda }$
Thus, as the applied voltage increases the SWL decreases.