ANS:B - get deflected by magnetic electric field.

The particle nature of cathode rays is proved due to the fact that they get deflected by magnetic and electric fields. Explanation: Cathode rays were discovered by J.J. Thomson in the late 19th century. Through his experiments with cathode ray tubes, Thomson demonstrated several properties of cathode rays that supported their particle nature:

1. Deflection by electric and magnetic fields: Cathode rays were observed to be deflected by both electric and magnetic fields. This behavior is characteristic of charged particles. When an electric field is applied, cathode rays are deflected in a direction that depends on their charge (positive or negative). Similarly, when a magnetic field is applied perpendicular to the path of the cathode rays, they are deflected in a direction perpendicular to both the magnetic field and the direction of motion, following the Lorentz force law. This deflection behavior is consistent with the behavior of charged particles, confirming the particle nature of cathode rays.
2. Production of fluorescence: When cathode rays strike a fluorescent material such as a phosphorescent screen, they cause the material to fluoresce or emit visible light. This fluorescence is a result of the kinetic energy of the high-speed cathode ray particles being transferred to the atoms or molecules of the fluorescent material, causing them to emit light. While the production of fluorescence is a characteristic behavior of cathode rays, it alone does not conclusively prove their particle nature.
3. Heat production: Cathode rays can also produce heat when they strike a material. This heat production is a result of the kinetic energy of the fast-moving cathode ray particles being converted into thermal energy upon impact with the material. Similar to fluorescence, while the production of heat is a characteristic behavior of cathode rays, it alone does not provide definitive evidence for their particle nature.

Overall, the most compelling evidence for the particle nature of cathode rays comes from their deflection by electric and magnetic fields, which is consistent with the behavior of charged particles such as electrons. Therefore, cathode rays are considered streams of charged particles, confirming their particle nature.