Further, the value of e/m was found to be
independent of the nature of the material/metal used as the cathode
(emitter), or the gas introduced in the discharge tube This observation
suggested the universality of the cathode ray particles Around the same time, in 1887, it was found that certain metals, when
irradiated by ultraviolet light, emitted negatively charged particles having
small speeds Also, certain metals when heated to a high temperature were
found to emit negatively charged particles