Final answer:
The statement is True; the term 'Useful Beam' does refer to X-rays that exit the Window of an X-ray tube.
Step-by-step explanation:
The statement "Useful Beam refers to X-rays exiting the Window of an x-ray tube" is True. When X-rays are generated in an X-ray tube, electrons are accelerated towards the anode by a high-voltage potential. The high-speed electrons collide with the anode, transferring their kinetic energy and producing X-rays. These X-rays then exit the X-ray tube through a special part known as the window, which is designed to allow the passage of X-rays while blocking other particles. The X-rays that successfully exit the window constitute the 'useful beam' that is then directed towards the subject being imaged, such as during diagnostic imaging in healthcare.