# Why does light have oscillating electric and magnetic fields?

I read in a book that according to The Theory Of Electromagnetic Waves, accelerated charged particles produce oscilating electric and magnetic fields, but how does light produce oscillating fields as it is neutral and massless? I am a high school student so please explain accordingly.

You are right when you say that accelerating particles produce, or radiate, electromagnetic waves. Light does not produce "oscillating fields", but rather it is itself an "oscillating field".

Light is composed by elementary particles called photons that can be interpreted as quanta (of perturbation) of the electromagnetic field.

You are also right when you say that light or rather the photon is massless, but it carries momentum.

• How does photon have momentum but it is considered massless? Apr 10, 2020 at 10:33
• @amaansiddiqui The following relativistic equation holds for any particle $E^2=p^2c^2 + m^2c^2$. If the mass $m$ is zero, we remain with $E^2=p^2c^2$, therefore if the energy $E$ of your photon is not zero, it carries a momentum $p$. Apr 11, 2020 at 8:35

Light does not produce these fields. Light is the oscillation in these fields (or, more accurately, the unified electromagnetic field). While this is a fair bit more advanced than high-school physics, one of the basic ideas behind quantum-field mechanics is that an excitation (read: wave) in a field can be considered as a particle or pseudo-particle. The particle associated with electromagnetic field is the photon, ie. a particle of light.

• Do you have a good link ? Apr 10, 2020 at 10:37
• For a primer on Quantum Field Theory at a relatively accessible level, I cannot recommend PBS Space Time enough: youtube.com/watch?v=ATcrrzJFtBY Apr 11, 2020 at 11:14
• @ D00M 1N8R Thank you very much. This was helpful. Apr 11, 2020 at 16:23

I think you may be looking at this from the wrong perspective.

Light doesn't exist as some fundamental entity and we have discovered that it produces oscillating fields.

Instead, there exists oscillating electromagnetic fields, and we call that phenomenon light.

Light doesn't create those oscillating field, it IS those oscillating fields.