I'm looking outside now and that's electromagnetic radiation - visible light.

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When it is ground into nanoparticles it can still block harmful ultraviolet radiation, but it allows visible light to pass straight though, which means modern sunscreens can appear completely transparent, while offering the same protection as the old white stuff.

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Even something too small to emit visible light will probably give off radio waves and infra-red radiation (Jupiter does).

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The telescope gathers and focuses electromagnetic radiation (usually, but not always, visible light) to make far-off objects seem brighter and closer.

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