Upper Energy Limit of Photon
Name: Andrew M.
Is there a theoretical upper limit to the energy of a photon?
Since wavelength decreases as energy increases is there a
"quantum limit" to the wavelength?
If there is no "theoretical limit" is there a practical limit based
upon our ability to detect a very high energy photon?
I am not aware of any limit to the energy of a photon. Energy is inversely
proportional to wavelength: as wavelength approaches zero, energy
approaches infinity. There are, however, two practical limiting factors to
photon energy. The first is the supply of energy. The universe may have a
great deal of energy, but it is not infinite. For a photon to exist,
something must produce it. The photon can not have more energy than that
which produced it. The second limit is particle creation. A photon
traveling through space has the ability to change into other forms. One
common occurrence is a photon transforming into an electron and a positron
(anti-matter electron). For this to happen, the photon must have enough
energy to create the mass of the particles (according to E=mc^2). It must
also have enough energy for some motion of the particles. The greater the
photon energy, the greater the number of things the photon can become. As a
result, a photon of greater energy is more likely to transform. These are
not quantum limits, but they are factors that make very high energy photons
Dr. Ken Mellendorf
Illinois Central College
Dear Andrew, As far as we know, there is no upper limit to the energy of
a photon, or of any other particle. The most energetic particles known at
the present time are observed in cosmic rays; they have energies which
extend up to over 10^20 eV (that is, of course, 1 followed by 20 zeroes).
What mechanism is capable of accelerating protons or photons to that
energy is not known. It is also interesting that they must be produced in
our astronomical neighborhood since at that energy the cross section for
interacting with a photon is very large and so, even though the microwave
background is very dilute, a proton or photon will collide with one and
lose some fraction of its energy before it has gone very far. "Very far"
here means some 150 million light years
Best, Dick Plano...
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Update: June 2012