Where do Photons Come From?
Most recent answer: 03/02/2014
- Travis Borstmayer (age 22)
Calgary, Alberta, Canada
Hi Travis,
As you say, ordinary atomic transitions don't have nearly enough energy to create gamma ray photons. Gamma ray photons tend to be produced during nuclear decays, which can release a lot more energy than electronic transitions. (You can also get gamma ray-photons from some other high-energy processes, like lightning. See the wikipedia page for for more.)
In general, photons can come from a huge variety of sources. Photons are just an excitation of electric and magnetic fields, so all you need is a process to provide energy and a means of converting another form of energy into light. Here are some examples.
Any accelerating electric charge, such as electrons in a wire, radiates light waves.
Another source of photons is from various particle interactions; as particles are destroyed or created, photons can be released as by-products.
Even imploding bubbles in a liquid can create light (see sonoluminescence on wikipedia).
In addition, photons can be split into multiple lower-energy photons, and the energy of a photon can be increased by, for example, bouncing it off of a moving mirror. Light can also gain or lose energy by scattering off atoms or materials in a non-resonant way (think deflected, not absorbed or emitted).
Hope that helps,
David Schmid
(published on 03/02/2014)