Final answer:
Cathode rays are streams of electrons that form when high voltage is applied in a cathode ray tube, and they can be deflected by magnetic and electric fields, indicating that they are negatively charged. Thomson's experiments showed that these electrons have a consistent mass-to-charge ratio irrespective of the tube's materials, demonstrating that electrons are fundamental constituents of atoms.
Step-by-step explanation:
Cathode rays are streams of electrons observed in vacuum tubes. When a high voltage is applied across electrodes in a tube containing gas at low pressure, it causes the gas to ionize and conduct electricity, resulting in a glowing beam. This beam is made up of particles moving from the cathode to the anode, which can be observed in a cathode ray tube (CRT).
English physicist J.J. Thomson's experiments in 1897 showed that these rays could be deflected by magnetic fields and electric fields, conclusively proving that cathode rays are made up of negatively charged particles, which are now known as electrons. Thomson's findings also revealed that the mass-to-charge ratio of these particles was consistent regardless of the material of the electrodes or the gas in the tube, indicating that electrons are fundamental components of atoms.
The deflection of cathode rays by an electric field supports the fact that they are negatively charged, as illustrated in scientific Figure 1.6.1. The rays are deflected away from a negatively charged field and toward a positively charged field because like charges repel and unlike charges attract. This behavior agrees with Coulomb's law, which states that the electrostatic force between two point charges is proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between the charges.