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When we speak of electromagnetic waves, we think of oscillating waves. But all disturbances need not be oscillating at a frequency. For example, if I take water, I could just lower the bottom plate and cause a cavity at the middle of a pool, and that disturbance would propagate outward as a decrease in amplitude, but not as an oscillating wave with a crest and a trough.

For electrons, I would imagine achieving this by uniformly accelerating a charge (as opposed to AC where the acceleration is sinusoidal, sawtooth, etc., so it accelerates and decelerates). It is only said that accelerating charges radiate, nothing is said about the mode of acceleration.

I understand that natural processes will be in the form of random vibrations, but as humans we are able to create DC for our purposes. I also know DC is fundamentally AC, but the ripple effect is minimal and it is the power that matters.

What is special about radiation with a frequency as opposed to other non-oscillating forms of radiation? Why do we always talk in terms of frequencies when referring to radiations?

Blacklight MG
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The light that comes from the sun comes in the form of oscillation of the EM field in the range of 100's of terahertz and our eyes evolved to take advantage of that.

There's nothing "wrong" with other forms of disturbance of the EM field, they're just not the ones that our eyes evolved to detect.

Why do we always talk in terms of frequencies when referring to radiations?

If you mean, why do we so often analyze disturbances of the EM field as combinations of sinusoidal (or complex exponential) disturbances, it's because the solutions to Maxwell's equations and the wave equation are easily found with these forms, and from Fourier analysis we know that these solutions can be used to construct any other solution we are interested in.

Furthermore, the complex exponentials (with sinusoids as a subset) are eigenfunctions of the wave equation, meaning that if we find a complex exponential solution for a problem at one point in space it's easy to find how this wave propagates to other points in space over time. With other forms of solution the easiest way to find how they propagate is to deconstruct them into complex exponentials using the Fourier transform, propagate those solutions, and then rre-construct the solution at the later time.

The Photon
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