Making estimates. Suppose that a proton-antiproton pair, at rest, annihilate
and create two photons. Using the data from the preceding exercise (i.e.
exercise 18.4), estimate
the frequency of each photon. A proton is nearly 2000 times more massive than
an electron.
Answer:
The energy of photons generated in the annihilation of an electron-positron
pair is equal to the total mass energy that is converted into photon energy.
The mass energy of an electron is about 0.511 MeV, so this is on the average
the
energy of each of the two photons. Using E=h f, with
, we find for the frequency
Since protons are about 2000 times (more precisely 1836 times)
more massive than electrons,
the photons from the annihilation of a proton/antiproton pair will have a
frequency about 2000 times as high.