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[Geltor]

I have a pretty basic understanding of the concept of electromagnetism, however one thing I still did not understand which prevents me from closing a full circle. I ask it here because the information I could find on the web describes things in a much too general way. I ask here because this forum is pretty lively and while I did submit my question on other forums it has been a week and I haven't received an answer from any of them.
I might be confusing many things here..so please be forgiving if i make a complete fool of myself.

My question is this:
As far as I am aware; radio waves, visible light, x-rays, and gamma rays belong to the same spectrum only that they have a different frequency/wavelength. Now, if we are able to generate radio waves using simple AC with the frequency we want, how is it that we aren't able to do the same with other types of electromagnetic rays? Why do we need to use cathodes to shoot electrons in microwave ovens to generate microwaves? Or why do we need to do the same process only have a chemical reaction with a certain metal with x-rays? Would it not be possible to generate every color of visible light ONLY by adjusting the frequency of AC current propagating through a wire? If not, why?

[LordBucket]

Would it not be possible to generate every color of visible light ONLY by adjusting the
frequency of AC current propagating through a wire?

According to google, yes. But you need an antenna on the order of ~300 nanometers long:

https://www.google.com/#q=optical+antennas
http://physics.stackexchange.com/questions/5046/can-i-use-an-antenna-as-a-light-source
http://www.technologyreview.com/view/514151/nano-scale-optical-antennas-could-have-a-big-impact/

[i2amroy]

Yeah, it's basically a problem with not being able to reliably manufacture and use antennas that are small enough to do what you want, and then the problem is amplified by the fact that if you want a noticeable effect you would need to have a huge amount of said antennas (since I doubt that a 1 nm antenna is going to put out much light amplitude.