# Can an object radiate ultraviolet light without also radiating in the visible spectrum?

**URL:** <https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733>\
**Category:** Factual Questions\
**Created:** [June 18, 2016, 10:26pm UTC](https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733 "2016-06-18T22:26:27Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [June 19, 2016, 1:15pm UTC](https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733/21 "2016-06-19T13:15:46Z")

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> [@Sunspace](#):
>
> So, imagine an object starting at room temperature and getting steadily warmer. To our eyes, it’s black, then dull red, then red, then orange, then yellow, then white. If it keeps warming up, will the emission peak move to the ultraviolet? When this happens, will the visible emissions continue to increase as well?

Yes and yes. Brightness in any given wavelength range increases as the temperature increases. A white-hot surface is emitting more red light than a red-hot surface.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [June 19, 2016, 6:47pm UTC](https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733/22 "2016-06-19T18:47:22Z")

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[A picture is worth a thousand words](https://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap18/F18-02%20Planck%20black%20body.jpg)

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**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\
**Post date:** [June 19, 2016, 11:17pm UTC](https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733/23 "2016-06-19T23:17:39Z")

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> [@scr4](#):
>
> Yes and yes. Brightness in any given wavelength range increases as the temperature increases. A white-hot surface is emitting more red light than a red-hot surface.

Thanks! I’ve wondered that for a long time.

I walked past some glass-blowing furnaces at Harbourfront today, and their working chambers were glowing a gorgeous, captivating, yet somehow also frightening, yellow. I thought of this thread.

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**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\
**Post date:** [June 24, 2016, 10:10am UTC](https://boards.straightdope.com/t/can-an-object-radiate-ultraviolet-light-without-also-radiating-in-the-visible-spectrum/757733/24 "2016-06-24T10:10:05Z")

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> [@Melbourne](#):
>
> In situations where the material is not re-absorbing all the energy it emits, you don’t get “black body” radiation.
> 
> Have I got this right?

I thought about this some more, and I was wondering why incadescent globes have a radiation distribution which, if not blackbody, certainly looks similar.

I realized is that metals are broad-band emitters and absorbers. Which lead me wonder what the emission spectrum of crystaline salt is? I suspect that it may be different from the flame emission spectrum, but I don’t know. Anyway, while looking around, I found that the National Bureau of Standards (now NIST) had considered the question:  
Selective Radiation from Various Solids  
[http://nvlpubs.nist.gov/nistpubs/bulletin/05/nbsbulletinv5n2p159\_A2b.pdf](http://nvlpubs.nist.gov/nistpubs/bulletin/05/nbsbulletinv5n2p159_A2b.pdf)

and  
[http://nvlpubs.nist.gov/nistpubs/bulletin/07/nbsbulletinv7n2p243\_A2b.pdf](http://nvlpubs.nist.gov/nistpubs/bulletin/07/nbsbulletinv7n2p243_A2b.pdf)  
Selective Radiation from Various Substances.

and also google specifically found lots of stuff about the emmission spectrum of the materials of lantern mantles

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