Which of the following radiations constitutes a stream of electrons?

Analyze the question: We need the radiation that is made of a stream of particles, specifically electrons, and not electromagnetic waves.

Explain the concept:

• Gamma rays (option A is typed "Ramma rays", which is a typo for gamma rays): high-energy electromagnetic waves from the nucleus. They are photons, not electrons.
• X-rays: electromagnetic waves produced when fast electrons hit a metal target. They are photons, not electrons.
• Cathode rays: a stream of electrons emitted from the cathode (negative electrode) of a discharge tube or vacuum tube. J.J. Thomson showed they are negatively charged particles, which are electrons.
• Radio waves: electromagnetic waves with the longest wavelengths in the spectrum. They are not particles.

Solution:

1. Gamma rays, X-rays and radio waves are all part of the electromagnetic spectrum. They are waves (photons) with no mass and no charge.
2. Only cathode rays are made of particles, and those particles are electrons.
3. Cathode rays are deflected by electric and magnetic fields in the direction expected for negative charges. This confirms they are electrons.

Answer: The correct option is C. Cathode rays.

Tip: Remember "Cathode = Electrons." Whenever you see an electromagnetic spectrum item (radio, microwave, infrared, visible, UV, X-ray, gamma), it is a wave, not a particle stream. Also keep in mind that beta particles are electrons too, while alpha particles are helium nuclei.