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

>but you can produce and receive one with a simple metal rod (antenna) and only the other can be focused with glass lens

Because different parts of the electromagnetic spectrum interact with different materials in different ways. Glass blocks UV and infrared but is transparent to every other part of the spectrum. Wood blocks visible light but is transparent to everything else.

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>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

This is just wrong. You most certainly do not need a LED or discharge tube to produce light. What do you think incandescent lightbulbs are? I mean hell, what do you think fire is? Is that not light? You can make light from a piece of wood. That’s much simpler than an amplifier circuit.