Fire and the Electromagnetic Spectrum

[hknight]

Hello.

 

I have an obscure question... I understand that electromagnetic energy spectrum includes everything from Gamma Rays to Radio waves, with x-rays, light and microwaves somewhere in between.

 

I also understand that fire releases energy. Much of this energy is heat, and some of it is light. In addition to light, what other forms of electromagnetic energy does a fire release?

 

Does a fire also emit ultra-violet radiation or infrared radiation? What about X rays and Microwaves? Or even radio wave interference?

 

And what would the distribution of this energy look like on a graph? I have attached an image of what I think it might look like, but I am probably way off base.

 

Thanks for your thoughts!

[insane_alien]

it will emit some ultra violet an even some x-rays but the amount is negligble most of the radiation emitted is in the infrared spectrum (heat basically) and there should also be a small amount of microwaves and radio. for the distrobution, look up "boltzman distrobution". the peak depends on the temperature of the fire.

[swansont]

As i_a mentioned, there is a distribution (Maxwell-Boltzmann). You can also search for blackbody and planck curve. In a fire you have a plasma, so there would likely be absorption and/or emission lines on top of the continuous spectrum, corresponding to quantum transitions in the atoms and molecules involved.

 

Also, you should notice there is no part of the EM spectrum marked "heat." All EM radiation emitted by a normal fire is heat. Typically the bulk of the radiation of what we consider to be hot is in the IR part of the spectrum.

[5614]

Expanding on what swansont said:

 

If you put your hand under a pure white light (ie. only white light, no IR or anything else) then your hand would still warm up. That is because light, as with all electromagnetic radiation (EMR), is energy. And energy makes you feel hotter*. So microwaves, like the ones which cook your food, would make you feel hot. So does IR, light, UV light and all EMR.

 

Very often when you talk about heat you are talking about IR light. For example body heat is IR. But saying "all heat is IR" can be misleading as explained above.

 

* more technically the energy of the light (photons) is absorbed by the atoms in your hand this makes the atoms vibrate faster. These vibrations are thermal energy (or heat). When something is hot (or has a lot of thermal energy) it means the atoms are vibrating quickly. When something is cold (little thermal energy) the atoms are vibrating slowly. The energy of any type of EMR is transferred to the atoms and makes them vibrate faster. So all forms of EMR can warm you up.

[swansont]

For example body heat is IR.

 

Body heat is largely IR, or peaked in the IR. People emit microwaves and radio waves, too.

[insane_alien]

People emit microwaves and radio waves, too.

 

*trys to microwave a burrito an broadcast a radio message with his hands.

 

its not working

[[Tycho?]]

Fire emits infrared mostly, some visible light. Negligible amounts of radiation in higher and lower parts of the spectrum.