Because higher frequencies radiate more easily, all sorts of special precautions are needed for electrical circuits which handle radio frequency current but none of those precautions are needed for circuits which handle 60 Hz household current.

Suppose that the electrons in an atom have just enough energy E = hf_vis to emit a burst of visible light.

A burst of ultraviolet light would need energy E = hf_uv which is much more than the atom has, so no ultraviolet light is emitted at all.

Examples --- What this is an example of

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