What is the difference between beta particles and cathode rays?

• A. Cathode rays originate inside an x-ray tube; beta particles originate from radioactive nuclei.
• B. Beta particles originate from radioactive nuclei; cathode rays originate inside an x-ray tube.
• C. Beta particles are photons; cathode rays are neutral.
• D. Beta particles have no mass; cathode rays have mass.

Answer: (B)

The key idea is where each particle comes from. Beta particles are electrons released during beta decay of unstable nuclei, so their origin is the atomic nucleus itself. Cathode rays are streams of electrons that originate at the cathode inside a vacuum tube and are driven by an applied voltage, such as in an x-ray tube. So, although both are electrons, their source differs: nucleus versus a cathode electrode.

They are not photons, and they do have mass, so statements claiming beta particles are photons or that they have no mass are incorrect. The distinction that cathode rays originate inside an x-ray tube describes a specific context, but the essential difference is that beta particles come from radioactive nuclei while cathode rays come from the cathode in a vacuum tube.