Why radio waves and light are fundamentally the same phenomenon of electromagnetic radiation, but you can produce and receive one with a simple metal rod (antenna) and only the other can be focused with glass lens?

Question

Also, why you can produce radio waves with a simple amplifier circuit and a piece of wire, but need special devices like an LED or a discharge tube to produce light?

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Answer 1

If you pump enough current through a metal rod it will be hot as hell and start glowing red and releasing visible light. I’m also guessing you could make an antenna out of something that is a good conductor but not a metal like carbon fiber.

Light can be “received” by a lot of things that aren’t glass lenses, it is just not useful for us to extract meaningful information from them.