Cathode rays are streams of electrons observed in vacuum tubes, i. e. evacuated glass tubes that are equipped with at least two electrodes, a cathode (negative electrode) and an anode (positive electrode) in a configuration known as a diode.
Izpi katodikoak huts- hodietako elektroi fluxu bat da. Huts- hodiak gutxienez bi elektrodo, katodo (elektrodo negatibo) bat eta anodo (elektrodo positibo) bat dituen hutsunedun beirako hodiak dira, diodo bezala ezagutzen den konfigurazioan.