Light, Photon Waves, and Electromagnetic Waves
Most recent answer: 04/26/2016
- Malay (age 15)
India
Yes, the role of these different descriptions of light can get confusing. The underlying exact description (so far as we now now) is that there's a quantum wave, a photon wave. It shouldn't be thought of as a collection of photons but rather as a wave with possibilities for a range of different numbers of photons, in the event that it happens to run into something like a photon-counting device. It also has a range of possible electromagnetic fields, if it happens to run into a field-measuring device. One peculiarity is that if the quantum wave has some exact number of photons, rather than a range, then the average electric field (also magnetic field) on repeated measurements of waves like that would be zero.
So the classical field description is an approximate description that works very well when the underlying field has lots of photons and the right sort of spread of possible photon numbers to give classical field behavior. Ordinary light sources usually are like that. You can also make beams with very different properties, well-defined numbers of photons and nothing like well-defined classical EM fields.
Mike W.
(published on 04/26/2016)