Discovery of Electron Quiz

Discovery of the Electron

• The electron was discovered by J.J. Thomson through the cathode ray discharge tube experiment.

Cathode Ray Tube Pressure Reduction

• Upon reducing the pressure inside the cathode ray tube to 0.01 mm Hg, cathode rays become visible, but the signal strength decreases.

Cathode Rays

• Rays emanating from the cathode and traveling in straight lines are referred to as cathode rays.

Anode Coating Material

• A fluorescent or phosphorescent material, such as zinc sulfide, is coated on the tube behind the anode to detect cathode rays.

Appearance of Dark Space

• A dark space near the cathode appears when the pressure in the cathode ray tube is lowered substantially, indicating the absence of visible light.

High Voltage Effects

• When a very high voltage (approximately 10,000 volts) is applied between the two electrodes at normal pressure, cathode rays are emitted, demonstrating their properties.

Observations with Fluorescent Materials

• Fluorescent or phosphorescent materials allow the visualization of cathode rays, glowing when they strike the material, showing the rays' path.

Behavior in Electric/Magnetic Fields

• Cathode rays are deflected by electric or magnetic fields, indicating that they possess charge and are influenced by external forces.

Composition of Cathode Rays

• Cathode rays consist of electrons, the subatomic particles responsible for carrying charge.

Properties of Electrons

• Electrons possess a negative charge and a small mass, enabling their identification and manipulation in experiments.

Charge-to-Mass Ratio

• The charge-to-mass ratio (e/me) of an electron is approximately -1.76 x 10^11 coulombs per kilogram, providing insights into its fundamental properties.

Millikan's Charge Determination

• R.A. Millikan determined the charge of the electron through the oil drop experiment, allowing for accurate measurement of charge and verifying its value as approximately -1.6 x 10^-19 coulombs.

Modification of Discharge Tube Experiment

• The discharge tube experiment was modified by W. W. Thomson (Lord Kelvin) through perforation of the cathode, enabling better observation of emitted rays.

E. Goldstein's Experiment

• According to E. Goldstein's experiment, when high voltage is applied between the two electrodes, additional rays known as anode rays or positive rays are emitted behind the perforated cathode.

Mechanical Work Capability

• Cathode rays possess kinetic energy, allowing them to perform mechanical work when interacting with obstacles, energizing surrounding materials.

Test your knowledge on the discovery of the electron by J J Thomson through the Cathode ray discharge tube experiment and its implications for understanding sub-atomic particles.