Question

In an X-ray tube, the intensity of the emitted X-ray beam is increased by
     A) Increasing the filament current
     B) Decreasing the filament current
     C) Increasing the target potential
     D) Decreasing the target potential

Answer 1

Hint: In an X-ray tube, electrons travel from the cathode to a heavy metal target which is the anode. Upon collision with the heavy target, they lose energy which is emitted in the form of X-rays. If somehow, the number of electrons increases, the number of emitted X-ray photons and hence, the intensity will also increase.

Complete answer:
An X-ray tube is a relatively simple electrical device which consists of a cathode filament and a heavy metal target which acts as the anode. When a potential is applied across the setup, electrons from the cathode filament get released from it, travel to and hit the heavy metal target anode. This causes a loss in their energy which is emitted in the form of X-ray photons.
Now, if the current in the filament is increased, the temperature of the filament will increase and there will be greater emission of electrons due to the greater thermal energy. Therefore, more electrons will hit the metal target in a time interval leading to release of a greater number of X-ray photons. This will essentially mean that the intensity of the X-rays will increase.
Therefore, the correct option is A) Increasing the filament current.

Note:
Students must note that changing the target potential will have no effect on the intensity of the photons released. Increasing the target potential means the electrons will have greater energy and upon collision, a greater energy may be transferred and hence higher energy photons will be released. However, there will be no change in the number of photons released in a time interval and hence, no change in the intensity of the emitted radiation.