The work function of a metal is the potential energy barrier height a conduction
ID: 1987625 • Letter: T
Question
The work function of a metal is the potential energy barrier height a conduction electron must surmount in order to leave the interior of the metal. In certain types of vacuum tubes the metal is shaped into a thin filament wire and heated until the kinetic energies of the electrons are sufficiently high to drive them out of the metal. In the photoelectric effect, photons supply the energy to emit the electrons out of the metal. In the case of field emission, how are the electrons able to escape the metal?(A) The electric field lowers the height of the potential barrier at the surface of the metal and outside the metal so the electrons can escape.
(B) The electric field lowers the height and narrows the width of the potential barrier outside the surface of the metal so the electrons can tunnel through.
(C) The electric field supplies the electrons with the potential energy needed to overcome the barrier.
(D) The electric field supplies the electrons with the kinetic energy needed to overcome the barrier.
(E) The electric field supplies the metal with the necessary voltage to allow the electrons to escape.
Explanation / Answer
(B) The electric field lowers the height and narrows the width of the potential barrier outside the surface of the metal so the electrons can tunnel through.
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