# Visible Light and Other EM Radiation

**URL:** <https://boards.straightdope.com/t/visible-light-and-other-em-radiation/6395>\
**Category:** Factual Questions\
**Created:** [January 18, 2000, 4:55pm UTC](https://boards.straightdope.com/t/visible-light-and-other-em-radiation/6395 "2000-01-18T16:55:00Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![Stephen](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@Stephen](https://boards.straightdope.com/u/Stephen)\
**Post date:** [January 21, 2000, 12:37am UTC](https://boards.straightdope.com/t/visible-light-and-other-em-radiation/6395/21 "2000-01-21T00:37:00Z")

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Pluto said…

> [@](#):
>
> BTW, the light generated by LEDs is created by laser action within the diodes. It is no longer coherent when emitted, however.

An LED produces photons by recombination. What do you mean by “laser action”. If the LED doesn’t have parallel surfaces capable of producing internal reflections, there is \*no resonator, no oscillation, no stimulated emmission, no amplification… (\*at least not at levels above those you’d find in any incandescent bulb)

> [@](#):
>
> And while tunable lasers are available, most of them operate at a specific frequency governed by the properties of the elements involved. Even the tunable ones only operate over a very narrow frequency band. No laser exists that is tunable across the entire visible spectrum.

## Well, no continuously tunable lasers per se… But, you can buy accessories that will output laser light continuously tunable from deep UV all the way through the far IR.

Stephen  
[Stephen’s Website](http://stephen.fathom.org)  
Satellite Hunting 1.1.0 visible satellite pass prediction  
shareware available for download at  
[Satellite Hunting](http://stephen.fathom.org/sathunt.html)

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