Difference Between Spectrum And Thermionic Emission
Spectrum, commonly the electromagnetic spectrum in which electromagnetic-wave radiations are arranged in order of frequency or wavelength. The entire electromagnetic spectrum is divided into regions within which the waves are generated or detected in a similar way. These regions include the radio-frequency spectrum, the infrared region, the visible-light spectrum, the ultraviolet region, and the X-ray region.
Thermionic Emission, the escape of electrons or ions from a heated solid or liquid. The escape of negative electricity from a hot solid was initially observed by Thomas Edison in 1883 during experiments with his evacuated carbon-filament lamp. This discovery was used by J. A. Fleming in 1904 to make the first electron tube. Since then, electron emission from hot solids has been particularly useful in radio and television tubes.
When a metal is heated, only some of its electrons acquire velocities high enough to escape to nearby space. Most of the work in escaping involves overcoming an electrostatic image force that tends to pull electrons back into the metal. This image force is reduced by applying a strong electron-accelerating electric field at the surface of the metal, thereby increasing the emission of electrons