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DUAL NATURE OF RADIATION AND MATTER — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsDUAL NATURE OF RADIATION AND MATTER2 Marks
Question
What is electron emission ? Explain its types.
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Answer

→"When electron in a metal possessing sufficient energy, the phenomenon of electrons leaving the metal is called electron emission."
 • Types of Electron Emission :
→The energy required to eject an electron from a metal can be given in different ways. There are three types of electron emission based on it.
(i) Thermionic emission :
→Properly heating the metal gives thermal energy to the electrons in it. By absorbing this energy, electrons can escape from the metal.
(ii) Field emission :
→Applying a very strong electric field (of the order of $10^8 Vm ^{-1}$ ) to the metal can pull electrons out of the metal.
(iii) Photo electric emission :
→When light of sufficient frequency is incident on a metal surface, electrons are emitted from the metal. This phenomenon is called photoelectric effect and the emitted electrons are called photo-electrons.

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