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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 the work function of metal? It depends on which factors?
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Answer

→Any metal has free electrons. These free electrons can move freely in the metal, hence they are responsible for the conductivity of the metal.
→However, these free electrons cannot escape from the metal surface. If an electron tries to come out of the metal, the metal surface acquires a positive charge which pulls the electron back to the metal.
→If the electron has enough energy to overcome the attraction of positive charge, it can escape from the metal.
→Thus, "The minimum energy required by an electron to escape from the metal surface is called the work function of given metal".
→It is denoted by $\phi_0$.
→The SI unit of wrok function is J. It is usually measured in eV (electron volt).
$\left(1 eV =1.6 \times 10^{-19} J\right. \text { ) }$
→$\phi_0$ depends on,
(i) type of metal
(ii) properties of metal and
(iii) type of surface.

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