Final answer:
In rotating anode tubes, the entire rotating disc is the target, central to the functioning of some X-ray tubes. The cathode ray tube (CRT) experiments showed that cathode rays are particles with mass and are capable of producing X-rays when electrons strike a target.
Step-by-step explanation:
In rotating anode tubes, the entire rotating disc is the target. This is a key component in the functioning of certain types of X-ray tubes frequently used in medical imaging and diagnostics. The principle behind these tubes is based on the acceleration of electrons towards a target material; upon impact, X-rays are produced due to the sudden deceleration of electrons. The use of a rotating anode allows for a larger target area for electron impact, which helps to dissipate heat more effectively compared to a stationary anode.
The concept originates from early experiments with cathode ray tubes (CRTs), where evidence like rotating paddle wheels within the tube suggested that cathode rays (electrons) must have mass since they carry enough momentum to cause mechanical motion. CRTs are found in older technology, such as non-flat-screen TVs and computer monitors, and they utilize magnetic fields to steer accelerated electrons to specific locations.