Where can gamma rays be detected?
Gamma-ray detectors can be placed in two broad classes. The first are what would typically be called spectrometers or photometers in optical astronomy. These are instruments which are “light buckets” and focus on a region of the sky containing the object of interest collecting as many photons as possible.
What is the frequency of a gamma ray?
Gamma rays have frequencies greater than about 10^19 cycles per second, or hertz (Hz), and wavelengths of less than 100 picometers (pm), or 4 x 10^9 inches. (A picometer is one-trillionth of a meter.)
Why are two gamma rays produced in annihilation?
When an electron and a positron (the electron’s antimatter counterpart) collide, they annihilate and disappear, giving off two gamma rays in the process. The particles appear to have vanished and all energy is transferred to the gamma rays (photons).
How do you find the minimum energy of a photon in pair production?
Therefore, the minimum energy of each photon, hfmin is given by equating the energy of the two photons, 2hfmin, to the rest energy of the positron and of the electron (i.e. 2hfmin = 2E0, where E0 is the rest energy of the electron.)
What is the minimum frequency of the photon that can produce an electron positron pair?
To produce two electrons, therefore, the photon energy must be at least 1.02 MeV. Photon energy in excess of this amount, when pair production occurs, is converted into motion of the electron-positron pair.
How are photons calculated?
Calculate the Energy of a Photon Often we use the units of eV, or electron volts, as the units for photon energy, instead of joules. You can use ​h​ = 4.1357 × 10-15 eV s, which results in a more reasonable energy scale for photons.
How do you emit a photon?
It is not the emission of an electron that produces a photon. A photon is produced when an electron releases energy by moving to a lower energy level within the atom. When the atom absorbs energy, it re-emits it in a random direction, almost instantaneously.