Crookes tube is a type of vacuum tube. William Crookes, an English physicist and chemist, developed the tube in the 1870’s as part of his study of what came to be called cathode rays. His work led to the discovery that these rays consist of streams of electrons.
A Crookes tube has low air pressure inside. At or near each end are two electrodes (electric conductors) called the cathode and the anode. When a strong electric current flows from the cathode to the anode, a glow appears in the end of the tube opposite the cathode. Crookes concluded that invisible rays from the cathode caused the glow. To study the rays, Crookes placed small objects in the rays’ path within the tube.
In 1879, Crookes suggested that the rays consisted of streams of negatively charged molecules. The English physicist Joseph John Thomson confirmed that the rays were charged particles of matter in 1897. Crookes tubes were forerunners of television picture tubes. Today, the Crookes tube is used only for classroom demonstrations.
