# 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? – amaan siddiqui Apr 10 '20 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 $p$. – Davide Dal Bosco Apr 11 '20 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 ? – Nikola Alfredi Apr 10 '20 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 – D00M1N8R Apr 11 '20 at 11:14
• @ D00M 1N8R Thank you very much. This was helpful. – Nikola Alfredi Apr 11 '20 at 16:23