What is the primary function of an x-ray (electron) tube?

The primary function of an x-ray (electron) tube is to convert electrical energy into x-ray radiation. This process occurs when high-energy electrons emitted from a cathode collide with a target material, typically made of tungsten, at the anode. The interaction of these high-speed electrons with the atoms of the target produces x-rays, which are then directed towards the area of interest for imaging.

Option B reflects this key role of the x-ray tube, as it emphasizes the conversion of electrical impulses into x-ray radiation, which is essential for generating images in various medical and industrial applications. This ability to transform electrical energy into radiation is fundamental to the operation of x-ray systems and is what enables clinicians to visualize internal structures non-invasively.

The other options do not accurately represent the primary function of the x-ray tube. High-frequency sound waves pertain to ultrasound technology, which is unrelated to x-ray imaging. While filtering out non-target radiation and regulating the density of x-ray beams are important aspects of improving image quality and safety in radiographic procedures, they are not the direct primary functions of the x-ray tube itself; rather, these are functions associated with auxiliary equipment or imaging techniques.