Which two electrodes are found within the evacuated glass envelope?

Within the evacuated glass envelope of an x-ray tube, the two key electrodes present are the cathode and the anode. The cathode is responsible for emitting electrons when heated, which occurs through a process called thermionic emission. This assembly typically includes a filament, which is heated to create a cloud of electrons around it.

The anode, on the other hand, serves as the target for the electrons emitted by the cathode. When these high-speed electrons collide with the anode, the kinetic energy is converted into x-rays as well as heat. The design of the x-ray tube, specifically the presence of these two electrodes, is fundamental to the production of x-rays in medical imaging.

The other combinations provided include elements such as neutrons and semiconductors, which do not belong to the functions of the electrodes within the x-ray tube. Neutrons are neutral particles found in atomic nuclei and play no role in the creation of x-rays. Similarly, semiconductors, while important in various electrical applications, do not function as electrodes in this context. Thus, the correct pairing of electrodes in the evacuated glass envelope of an x-ray tube is indeed the cathode and anode.