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*Applet Tutorial*

- On the left hand side, the Fermi function f(E) is plotted. On the right
hand side, discrete states (localized states) are shown. For E > E
_{F}, f(E) approaches zero. This means that the energy states are vacant (no electron occupies the state). For E < E_{F}, f(E) approaches unity. This means that an energy state is occupied by an electron with certainty. - Use mouse to drag E
_{F}up or down. Observe the electron occupying or vacating the states. The probability function f(E) is only relative to E_{F}. E_{F}is called the Fermi level and is the central parameter in deciding the number of electrons at a given energy E. - Change the Temperature using the scroll bar at the bottom of the applet. Observe its effect on f(E) and on the electron distribution. At a higher T, the electron distribution is more gradual: the electron number changes more slowly with E. This is because the higher thermal energy kT promotes more electrons from lower states to higher states.