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Chapter 2: Problem 13

Summarize the evidence used by J. J. Thomson to argue that cathode rays consist of negatively charged particles.

Short Answer

Expert verified
J.J. Thomson's experiments provided evidence that cathode rays consist of negatively charged particles by observing their deflection in both magnetic and electric fields, measuring their high charge-to-mass ratio, and demonstrating that their properties remained consistent regardless of the cathode material or gas used in the experiment. This led him to conclude that the negatively charged particles in the cathode rays were a universal component of all matter.

Step by step solution

01

Understand J.J. Thomson's Experiment with Cathode Rays

J.J. Thomson conducted a series of experiments using Cathode Ray Tubes (CRTs) to study the properties of cathode rays. These experiments involved applying a magnetic and electric field within the CRT and observing the trajectory of the rays.
02

Magnet Deflection of Cathode Rays

In his experiments, Thomson observed that when a magnet was brought near the cathode ray tube, the cathode rays were deflected by the magnetic field. From this observation, he concluded that cathode rays must have an electric charge, as they interact with the magnetic field.
03

Electric Field Deflection of Cathode Rays

Thomson also subjected the cathode rays to an electric field. He found that the rays were deflected by the electric field, and the direction of deflection indicated that the rays carried a negative charge (they were attracted towards the positive electrode).
04

Mass-to-Charge Ratio of Cathode Rays

By carefully measuring the amount of deflection of the cathode rays under known magnetic and electric fields, Thomson was able to determine the mass-to-charge ratio (m/e) of the particles in the cathode ray. His measurements revealed that these particles had a much higher charge-to-mass ratio than any previously known charged particle (such as the hydrogen ion).
05

Cathode Ray Particles are Universal

Thomson performed experiments with different cathode materials and gases inside the CRT, and found that the properties of the cathode rays remained the same regardless of the material used or the gas inside the tube. This led him to conclude that the negatively charged particles in the cathode rays were a fundamental and universal component of all matter.
06

Conclusion

J.J. Thomson's experiments with cathode ray tubes provided the following evidence supporting the idea that cathode rays consist of negatively charged particles: 1. Cathode rays are deflected by both magnetic and electric fields, indicating they have an electric charge. 2. The direction of deflection in an electric field suggests the charges are negative. 3. The particles in cathode rays had a much higher charge-to-mass ratio than any previously known charged particle. 4. The properties of the cathode rays did not change with different cathode materials or gases, suggesting that the negatively charged particles are a universal component of all matter.

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