PHYS 1C Lecture Notes - Lecture 19: Arthur Compton, Work Function, Photon
A photon's energy would be given by: E= hf
-
Each photon can give all its energy to an electron
in the metal
-
This electron is now called a photoelectron (since
a photon released it)
-
The energy needed to release the electron from
the metal is known as the work function, phi.
-
If the energy of the photon is less than the work
function of the metal then the electron will not be
liberated
-
But if the energy of the photon is greater than the
work function of the metal than the electron will
be liberated and given kinetic energy, as well.
-
The maximum kinetic energy of the liberated
photoelectron is:
-
Photoelectric effect
The maximum kinetic energy depends only on the frequency and
the work function, not on intensity.
-
How tightly bound the electrons are to the metal
○
The work function itself tells you about the metal and how
much energy is required to liberate an electron
○
The KE of the electron will depend on the work function,
but what the work function is not related to the KE of the
electrons
○
What does the work function measure?
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Work Function
In 1923, Arthur Compton directed a beam of X-rays toward a
block of graphite
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He detected that some of the scattered X-rays had a slightly
longer wavelength than the incident X-rays
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This means those scattered photons had less energy than the
incident photons
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The amount of energy those scattered lost depended on the
angle at which the X-rays were scattered
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This change in wavelength is called the Compton Shift
-
To calculate the shift in wavelength, Compton assumed that the
photons act like other particles in collisions
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In the collisions, energy, hf, and momentum, hf/c, were
conserved
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The energy of the incoming photon was
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The Compton Effect
(19) Lecture 28A: Wave-particle duality
Monday, May 21, 2018
12:55 PM
week 8 Page 1
Document Summary
A photon"s energy would be given by: e= hf. Each photon can give all its energy to an electron in the metal. This electron is now called a photoelectron (since a photon released it) The energy needed to release the electron from the metal is known as the work function, phi. If the energy of the photon is less than the work function of the metal then the electron will not be liberated. But if the energy of the photon is greater than the work function of the metal than the electron will be liberated and given kinetic energy, as well. The maximum kinetic energy of the liberated photoelectron is: The maximum kinetic energy depends only on the frequency and the work function, not on intensity. How tightly bound the electrons are to the metal. The work function itself tells you about the metal and how much energy is required to liberate an electron.
