# Light emission/absorption

**URL:** <https://boards.straightdope.com/t/light-emission-absorption/247243>\
**Category:** Factual Questions\
**Created:** [May 26, 2004, 9:42pm UTC](https://boards.straightdope.com/t/light-emission-absorption/247243 "2004-05-26T21:42:10Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![GreyWanderer](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@GreyWanderer](https://boards.straightdope.com/u/GreyWanderer)\
**Post date:** [May 26, 2004, 9:42pm UTC](https://boards.straightdope.com/t/light-emission-absorption/247243/1 "2004-05-26T21:42:10Z")

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When light is reflected off a wall, some wavelengths are absorbed, while some are reflected, creating the color of the wall. I assume the absorbed photons make electrons in the wall jump to higher orbitals. But want they immidiatly fall down and emit a photon of the same wavelength again? What am I missing here?

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**Author:** ![Punoqllads](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@Punoqllads](https://boards.straightdope.com/u/Punoqllads)\
**Post date:** [May 26, 2004, 11:15pm UTC](https://boards.straightdope.com/t/light-emission-absorption/247243/2 "2004-05-26T23:15:28Z")

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The energy absorbed by the electron makes it go up to a higher unocupied orbital, but any electron can then jump down to the vacated spot, releasing a photon of a (presumably) longer wavelength than the original photon. Electrons above the now-vacated spot can then jump down into that spot, etc. That’s why blackbodies luminated by visible light emit photons in the infrared spectrum.

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**Author:** ![Bag\_of\_Mostly\_Water](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bag_of_mostly_water/32/1029_2.png) [@Bag\_of\_Mostly\_Water](https://boards.straightdope.com/u/Bag_of_Mostly_Water)\
**Post date:** [May 26, 2004, 11:21pm UTC](https://boards.straightdope.com/t/light-emission-absorption/247243/3 "2004-05-26T23:21:56Z")

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Some will; this is called “fluorescence.” If the molecules which make up the wall coating hold the energy for some time and then release it as light, it is called Phosphorescence.

However, compounds that fluoresce and phosphoresce are rather rare. Most of the molecules which make up the wall coating will probably drop the energy into heat – so the wall warms up. You can easily feel this if the light is strong enough.