J.J. Thomson's cathode-ray tube experiment didn't directly "show" anything in the way we might think of a demonstration. Instead, it was a series of experiments that allowed him to *deduce* the existence of the electron and measure its properties. Here's what he did and the significance of the findings:

The Experiment:

* Cathode Ray Tubes: Thomson used cathode ray tubes, which are glass tubes with a vacuum inside. He applied a high voltage across the tube, creating a beam of light that emanated from the negative electrode (cathode).

* Magnetic Fields: He placed magnets near the beam and observed that the beam deflected, indicating that it was carrying a charge.

* Electric Fields: He then applied an electric field to the beam. The beam deflected again, but this time in a direction opposite to the magnetic field deflection.

* Measuring Deflection: He carefully measured the amount of deflection caused by both electric and magnetic fields.

The Key Deductions:

1. Electrons as Particles: Thomson concluded that the cathode rays were made up of tiny negatively charged particles he called "corpuscles" (later named electrons).

2. Charge-to-Mass Ratio: By analyzing the deflection patterns in both magnetic and electric fields, he was able to calculate the charge-to-mass ratio (e/m) of the particles. This ratio was significantly smaller than that of any known ion, indicating that these particles were much lighter.

3. Universality of Electrons: He found that the e/m ratio was the same regardless of the material used for the cathode, suggesting that these particles were fundamental constituents of all matter.

Significance:

Thomson's experiment revolutionized our understanding of atoms:

* Subatomic Particles: It proved that atoms are not indivisible, as previously thought, but contain smaller particles with their own charges and masses.

* Electron Discovery: The discovery of the electron was a groundbreaking achievement, laying the foundation for future research in atomic physics.

* Foundation for Modern Physics: Thomson's work paved the way for models of the atom like the "plum pudding" model and later, the Bohr model.

In summary, J.J. Thomson's cathode-ray tube experiment didn't show a specific event or phenomenon directly, but rather provided evidence and allowed him to deduce the existence and properties of the electron, a fundamental building block of matter.