Q.Cathode rays are group of (A) electrons
(B) protons
(C) neutrons
(D) atoms

Cathode rays are a stream of negatively charged particles — electrons — emitted from the cathode.

In a discharge tube at low pressure, rays travel from the cathode to the anode. J. J. Thomson showed by their deflection in electric and magnetic fields that these rays are negatively charged particles with a very large charge-to-mass ratio, inde …

Electron emission driven by heating a metal surface is called thermionic emission, distinct from photoelectric (light-driven) or field (strong-electric-field-driven) emission.

Working

Electrons can be emitted from a metal surface by supplying energy in different forms:

• Thermionic emission -- electrons gain enough energy to escape by being heated (thermal energy), as in the heated filament/cathode of a vacuum tube or CRT.
• Photoelectric emission -- electrons are emitted when light of sufficient frequency falls on the surface.
• Field emission -- electrons are pulled out by a very strong external electric field. …

Cathode rays are a beam of electrons → option (A).

Cathode rays are produced in a discharge tube at low pressure and travel from the cathode toward the anode. They were shown by J. J. Thomson to be deflected by electric and magnetic fields in a way that identifies them as a stream of negatively charged p …

Electron emission triggered specifically by heat absorption is called thermionic emission, distinct from photoelectric (light-triggered), secondary (particle-impact-triggered), or field (strong-field-triggered) emission.

Working

Different mechanisms can supply the energy needed for electrons to escape a metal surface (overcoming its work function):

• Thermionic emission: electrons are emitted when the metal is heated, giving them enough thermal kinetic energy to escape (used in vacuum tube cathodes, CRTs).
• Photoelectric emission: electrons are emitted when light (photons) of sufficient frequency falls on the metal surface. …

J.J. Thomson's experiments on cathode rays (deflection in electric and magnetic fields, and charge-to-mass ratio measurement) established that they are streams of negatively charged particles — electrons.

Working

Cathode rays are streams of particles emitted from the cathode in a discharge tube at low pressure. J.J. Thomson's classic experiments showed that:

• Cathode rays are deflected towards the positive plate in an external electric field, and their deflection in a magnetic field follows the pattern expected for negatively charged particles. …