Science Forums 2

[CraigD]

Described in terms of particles, both light and magnetic fields are made of photons. In their role as carriers of magnetic force, photons can affect only particles with non-zero charge. Photons have zero charge, so can’t be effected by the magnetic force they carry – in other words, photons can’t affect one another’s momentum.

Force carriers – bosons - are essentially momentum carriers. In addition to their role as magnetic force carriers, photons carry momentum in their role as radiation. The most common example of photons in this role is in carrying momentum from electrons in glowing atoms, which then change to a lower energy orbital, to electrons that absorb them, changing to higher energy orbitals, or separating – ionizing – them from their atoms altogether.

There’s an important, difficult to explain difference between the formal nature of photons as magnetic force and as light, which is too involved to explore in detail in a Q&A thread. To explore more, browse information about virtual particles. In the role of magnetic force carrier, photons are virtual. In their role as radiation, they are not.