15. The diagram shows an electric circuit including a photocell.
The photocell contains a metal plate X that is exposed to
electromagnetic radiation. Photoelectrons emitted from the
surface of the metal are accelerated towards the positive
electrode Y. A sensitive ammeter measures the current in the
circuit due to the photoelectrons emitted by the metal plate
X. The metal plate X has a work function of 2.2 eV. The
maximum kinetic energy of an emitted photoelectron from
this plate is 0.3eV.
G
Electrong
radiation
H
vacuum
a) Calculate the energy of a single photon in eV and in joules.
b) Calculate the frequency of the incident electromagnetic radiation.
c) Deduce the effect on the current if the radiation has the same intensity, but the frequency is
greater than in (b).
16. A negatively charged metal plate is exposed to electromagnetic radiation of frequency (f). The
diagram below shows the variation with (f) of the maximum kinetic energy KEmax of the
photoelectrons emitted from the surface.