Microwave Heating -- 2.4GHz in, IR radiation out....

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SUMMARY

The discussion centers on the operation of microwave ovens at a frequency of 2.4 GHz, specifically in the context of heating water to 100°C (373K) for beverages like tea and coffee. It highlights the conversion of microwave energy into infrared radiation, with materials absorbing microwave photons and subsequently emitting significantly more energetic infrared photons. The conversation also addresses misconceptions about photon upshifting processes, clarifying that the energy transfer is a classical electromagnetic wave interaction rather than a resonant process.

PREREQUISITES
  • Understanding of electromagnetic waves and their properties
  • Familiarity with Planck's law and Wien's law
  • Knowledge of thermal energy transfer mechanisms
  • Basic concepts of photon interactions, including the Raman Effect
NEXT STEPS
  • Research the principles of electromagnetic wave interactions with matter
  • Study Planck's law and its applications in thermal radiation
  • Explore the mechanics of thermal energy conversion in materials
  • Investigate the differences between resonant and non-resonant photon interactions
USEFUL FOR

Physicists, engineers, and anyone interested in the principles of microwave heating and thermal radiation processes.

Anand Sivaram
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Microwave oven operates at 2.4 GHz. Consider the situation of making tea or coffee in Microwave where water is heated to 100C to boil.

Looking at Planck's law / Wien's law, 100C (373K) corresponds to a peak wavelength of 7.8nm or 38.6THz which is in Mid Infrared.

Effectively materials absorb microwave photons and re emit 15000 times more energetic IR photons.

How is this taking place? Is it similar to Anti Stokes shift, Raman Effect etc. where photon upshifting could take place.

Thanks and Regards

Anand
 
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Anand Sivaram said:
How is this taking place? Is it similar to Anti Stokes shift, Raman Effect etc. where photon upshifting could take place.
No, you couldn't have such a process involving so many photons.

I wouldn't even talk about microwave photons, as the process is not resonant. It is more a classical EM wave that transfers energy to the water molecules which heat up (radiation energy is converted into rotational, vibrational, and translational motion) and that thermal energy is then re-radiated as IR.
 

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