Final answer:
Cathode rays are streams of negatively charged electrons emitted from the cathode in a cathode ray tube and are significant for proving the existence of electrons with a charge-to-mass ratio of 1.8 × 10^8 Coulombs/gram, as discovered by J.J. Thomson.
Step-by-step explanation:
Cathode rays, discovered during experiments with cathode ray tubes, are streams of electrons that emanate from the cathode (a negatively charged electrode) when electricity is applied. These rays are affected by magnetic fields and electrical fields, revealing their negative charge. In fact, they are deflected by a magnetic field, illustrating the interaction between charged particles and magnetic fields. Cathode rays are also deflected away from a negatively charged field and attracted towards a positively charged field, which demonstrates the negative charge of the particles in the rays.
Experiments by English physicist J.J. Thomson were pivotal in determining the nature of cathode rays. One significant discovery he made was that the charge-to-mass ratio of the electron, found in cathode rays, is 1.8 × 108 Coulombs/gram. This was a foundational discovery that suggested electrons were a fundamental component of atoms, thereby transforming our understanding of atomic structure.
Additionally, an experiment involving a paddle wheel indicated that the cathode ray had mass since it could move the wheel along the rail, implying not just a presence of charge but also of mass. Early research, including the work of Sir William Crookes, helped lay the groundwork for these discoveries by exploring these mysterious rays and establishing them as a stream of particles.