Is it possible to create magnetic waves?
Category: Physics Published: January 13, 2016
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Assistant Professor of Physics at West Texas A&M University
Yes, it is possible to create electromagnetic waves using magnets. No, it is not possible to create magnetic waves without an electric field being present. Electric fields are created by electric charges. For instance, if you statically charged up a balloon by rubbing it on your hair, the balloon creates an electric field. Magnetic fields are created by magnets. For instance, a fridge magnet creates a magnetic field and uses it to stick to your fridge. Electric fields and magnetic fields are not separate entities. They are really facets of one unified entity: the electromagnetic field.
While electric charges can create electric fields, magnetic fields can also create electric fields. Similarly, while magnets can create magnetic fields, electric fields can also create magnetic fields. In fact, every time you change a magnetic field, you create an electric field. This is called Faraday's Law of Induction. Similarly, every time you change an electric field, you create a magnetic field. This is called the Maxwell-Ampere Law. The interesting thing is that a changing electric field creates a changing magnetic field, which creates a changing electric field, which creates a changing magnetic field, and so on. Rather than view the electric field and magnetic field as separate entities that constantly create each other in a cyclical feedback process, it is more accurate to view them simply as one unified object: the electromagnetic field. Because of this cyclical feedback process, electromagnetic fields that vary in time become self-sustaining and propagate themselves out into space, even if the electric charges or magnets that started the process are taken away. We call such self-sustaining variations in the electromagnetic field "electromagnetic waves" or "electromagnetic radiation." A familiar example of electromagnetic waves is visible light. All electromagnetic waves travel at the speed of light because they are all effectively light of one kind or another.
So no, it is not possible to create purely magnetic waves. The very act of creating waves in the magnetic field automatically creates corresponding electric fields and leads to electromagnetic radiation. For instance, if you grab a bar magnet and shake it back and forth above your head, you don't create magnetic waves. You create electromagnetic waves. More specifically, you create very weak, very low-frequency radio waves. This is not a figure of speech. The act of waving around a bar magnet literally creates radio waves that shoot out in all directions. However, these radio waves are very low-frequency, so don't think you can start broadcasting new-age music to your radio receiver by waving around a bar magnet.