How to emit 3.2 micrometer wavelength

  • Context: Undergrad 
  • Thread starter Thread starter Vincent L
  • Start date Start date
  • Tags Tags
    Wavelength
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
12 replies · 2K views
Vincent L
Messages
7
Reaction score
3
Good day!
Can anyone tell me how to emit a 3.2 micrometer(μm) wavelength with as much energy as possible? How could it be "homemade"? Is it possible?
Thank you so much
 
Physics news on Phys.org
Welcome to PF. :smile:

What is the application? How much power are we talking about here? It looks to be in the IR part of the EM spectrum, right?

1654103904106.png

http://www.pas.rochester.edu/~blackman/ast104/spectrum.html
 
Thank you for taking the time. My english is limited.
So i want it conceiled in a box. I want to reflect the emission so it can heat the molecules i put in the box as much it is possible.
 
  • Wow
Likes   Reactions: davenn
Maybe the hot filament of a lamp. You can adjust the operating voltage so that IR is emitted without visible light. I use this to demonstrate the Greenhouse Effect, by altering the temperature to give long and short wavelength IR. At long wavelengths, radiation actually comes from the hot glass of the bulb, as the glass is opaque to long wavelengths.
 
  • Like
Likes   Reactions: Vincent L
It seems to me you want a blackbody cavity with walls ~900K
guest631096994.png
 
  • Like
Likes   Reactions: Vincent L
Thank you all. I believe this to match with my questionning. I hope you all a good day
 
  • Like
Likes   Reactions: bob012345
tech99 said:
Maybe the hot filament of a lamp. You can adjust the operating voltage so that IR is emitted without visible light. I use this to demonstrate the Greenhouse Effect, by altering the temperature to give long and short wavelength IR. At long wavelengths, radiation actually comes from the hot glass of the bulb, as the glass is opaque to long wavelengths.
Thank you!
 
The problem is that the OP refers to a specific wavelength. All the above answers seem based on the assumption of a black body spectrum. If the OP were referring to spectral yellow wavelength or, say a millimetre radio wavelength, the answers would not have assumed thermal radiation.
What is it about a 3.2 micron wavelength that makes us assume that it's not monochromatic?
@Vincent L could you tell us about your choice of that particular wavelength and some more detail about your proposed experiment?
 
  • Like
Likes   Reactions: hutchphd
sophiecentaur said:
The problem is that the OP refers to a specific wavelength. All the above answers seem based on the assumption of a black body spectrum. If the OP were referring to spectral yellow wavelength or, say a millimetre radio wavelength, the answers would not have assumed thermal radiation.
What is it about a 3.2 micron wavelength that makes us assume that it's not monochromatic?
@Vincent L could you tell us about your choice of that particular wavelength and some more detail about your proposed experiment?
I want to CO2 to absorb it in ambient air, in a box. I want it to transfert heat to the other molecules. So I am taking the CO2 spectrum that is absorbed but not the rest Thank you for taking time
 
Vincent L said:
I want to CO2 to absorb it in ambient air, in a box. I want it to transfert heat to the other molecules. So I am taking the CO2 spectrum that is absorbed but not the rest Thank you for taking time
Can you post a link to the ##3.2 \mu m## number that you posted? I'm finding different peaks for CO2 absorption specta...
 
berkeman said:
Can you post a link to the 3.2μm number that you posted? I'm finding different peaks for CO2 absorption specta...
It seems to me that the OP is trying to measure the mechanism of the 'greenhouse effect'. Atmospheric absorption of IR is a very small effect, for a short path distance (i.e. a 'box'). It's pretty subtle even over the tens of km of the path through the atmosphere and many years of input power. If the effect were really that obvious we wouldn't be having difficulties with the climate change deniers.

@Vincent L 's idea is more of a thought experiment than one which would be practical. It would involve measuring a tiny temperature change, probably involving comparative readings for a box of CO2 and one with the equivalent mass of CO2-free air. A source of narrow band IR energy could be a filtered halogen or LED source, such as you can get for back pain relief. An IR photography floodlight wouldn't have the necessary power, although the spectrum could be better.

It's a good topic for discussion though and throws up a lot pf practical factors about this sort of measurement.