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This question already has an answer here:

After watching a few videos on light and electromagnetic radiation, I am a little confused.

The way things are explained, is that light is just the same as electromagnetic radiation I thought this would be strange as then microwaves and radios would also be called light. Plus, I am not sure of the origin of the word photon, but in Japanese which I use it is 光子 which kind of translates to light molecule.

I found an answer to this:

electromagnetic radiation to which the organs of sight react, ranging in wavelength from about 400 to 700 nm (http://dictionary.reference.com/browse/light?s=t)

However, after searching the web it seems that this is approximately the same spectrum for humans. So, is there a difference between light and visible light? If not, why use visible light?

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marked as duplicate by jinawee, John Rennie, Brandon Enright, Kyle Kanos, Qmechanic May 4 '14 at 23:54

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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There is no difference between light and visible light. English use of the word light is based on an understanding that predates fundamental scientific description of light and photons. However, it would be generally interpreted that if you say, "The light from the stars shines down on us" would mean visible light.

A physicist discussing light shining from a star could mean the entire spectrum of photon energies, including visible light. The term visible light is specific to the photon energies that are visible to human beings. When discussing photons with other energy levels, it is not uncommon for physicists to talk about the photons as light, even if it is not visible to the human eye.

Not including the word "visible" is primarily a short-cut.

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  • $\begingroup$ So using the terms "ultra-violet light" or "infra-red light" is a contradiction? $\endgroup$ – DJohnM May 4 '14 at 15:52
  • $\begingroup$ No, ultra-violet and infra-red in this case are adjectives and describe the general range of the frequencies of the particular photons or light. $\endgroup$ – C G-K May 4 '14 at 20:06
  • $\begingroup$ Thanks. It seems the word "light" is not very scientific. It appears a lot in videos discussing related topics though. Is "light" used in more scientific papers? $\endgroup$ – Damien Golding May 5 '14 at 3:51
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The word "light" usually refers to the range of electromagnetic radiation from ultraviolet light through infrared light. So light includes, ultraviolet light, visible light and infrared light. Radio waves, microwaves, x-rays and gamma rays are electromagnetic radiation, but are not usually referred to as "light", even though there is no fundamental difference.

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