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

In summary, the conversation discusses the operation of a microwave oven at 2.4 GHz and the process of heating water to 100C for making tea or coffee. This temperature corresponds to a peak wavelength of 7.8nm or 38.6THz in the Mid Infrared range, and materials absorb microwave photons and re-emit more energetic IR photons. This process is not similar to Anti Stokes shift or Raman Effect, as it does not involve photon upshifting. Instead, it is a classical EM wave that transfers energy to water molecules, which then heat up and re-radiate as IR.
  • #1
Anand Sivaram
90
43
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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  • #2
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.
 

1. How does microwave heating work?

Microwave heating uses electromagnetic waves with a frequency of 2.4GHz to agitate water molecules in food, causing them to vibrate and generate heat. This heat then cooks the food from the inside out.

2. Is microwave heating safe?

Yes, microwave heating is generally considered safe for cooking food. The radiation used in microwaves is non-ionizing, meaning it does not have enough energy to damage DNA or other molecules in the body.

3. What types of materials can be heated in a microwave?

Most food and liquid items can be heated in a microwave, as well as some heat-resistant materials like glass and ceramic. However, metal and aluminum foil should not be used in microwaves as they can cause sparks and potential fire hazards.

4. How does microwave heating compare to other forms of heating?

Microwave heating is generally faster and more efficient than conventional heating methods like ovens or stovetops. It also does not require preheating and can heat food more evenly.

5. Can microwaves be used for more than just heating food?

Yes, microwaves have various other applications such as in telecommunications, radar, and medical treatments. They can also be used for tasks like drying and sterilizing objects, and in industrial processes.

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