Question

Whtvis electric discharge?how it occurs?

Answer 1

Explanation:

Electric discharge denotes the excitation of atomic states in a gaseous medium on passing an electric current through the medium. An ordinary household fluorescent lamp is an example of an electric-discharge source. The lamp tube, coated on the inside with fluorescent phosphors, contains a mixture of a rare gas and mercury vapour. On application of sufficiently high voltage across the lamp's terminals, a low-pressuremercury arc forms. Thus, excited Hg atoms emitUV radiation (a particularly strong line exists at 253.7 nm) which is absorbed by the phosphor and re-emitted as visible light. The phosphor radiation spectrum is concentrated in the visible spectral region; it is smooth with several superimposed discrete lines originating in the Hg atoms.