Thursday 14 March 2013

PHOTOELECTRIC EFFECT - Q11

11) Interpret thermionic emission in light of photoelectric effect.
Ans: Thermionic emission is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier using photoelectric effect. This occurs because the thermal energy given to the carrier overcomes the binding potential, also known as work function of the metal. The charge carriers can be electrons or ions. After emission, a charge will initially be left behind in the emitting region that is equal in magnitude and opposite in sign to the total charge emitted. But if the emitter is connected to a battery, then this charge left behind will be neutralized by charge supplied by the battery, as the emitted charge carriers move away from the emitter, and finally the emitter will be in the same state as it was before emission. The thermionic emission of electrons is also known as thermal electron emission.

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