I want to start by saying that I understand some of the stuff and I guess this should be more of an explanation like I’m 10 or 15. I know polar molecules and heat result from kinetic energy among molecules in rotation, vibration, and translation so I kind of get that dielectric heating works by moving the molecules around. I also understand light waves and frequency and some basic circuitry. The thing that I struggle to understand is the choice in frequency for microwaves. What makes other nonionizing frequencies not as good as microwaves and how is it able to release so much energy/food absorbs so much energy with low-frequency waves.
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Molecules are very small, not much bigger than the size of visible light waves. It’s difficult to convert large amounts of electricity into these wavelengths of light efficiently. And the light wouldn’t penetrate the food very deeply. The 2.45 GHz radio waves commonly used in microwave ovens can be generated efficiently with a magnetron tube. They also couple well into the water contained in the food, so the food is quickly heated through. There are other higher frequencies that also work well to cook food. The industry has settled on 2.45 GHz because it’s easier to build this size of magnetron.
Molecules are very small, not much bigger than the size of visible light waves. It’s difficult to convert large amounts of electricity into these wavelengths of light efficiently. And the light wouldn’t penetrate the food very deeply. The 2.45 GHz radio waves commonly used in microwave ovens can be generated efficiently with a magnetron tube. They also couple well into the water contained in the food, so the food is quickly heated through. There are other higher frequencies that also work well to cook food. The industry has settled on 2.45 GHz because it’s easier to build this size of magnetron.
Molecules are very small, not much bigger than the size of visible light waves. It’s difficult to convert large amounts of electricity into these wavelengths of light efficiently. And the light wouldn’t penetrate the food very deeply. The 2.45 GHz radio waves commonly used in microwave ovens can be generated efficiently with a magnetron tube. They also couple well into the water contained in the food, so the food is quickly heated through. There are other higher frequencies that also work well to cook food. The industry has settled on 2.45 GHz because it’s easier to build this size of magnetron.
If the light *has* to be nonionizing, then we’re essentially stuck with:
1. Visible light. This does not penetrate super well into food, is hard to generate in necessary quantities. It would also be blinding if you *did*. This would just sear the surface if you tried to cook too fast with it.
2. Infrared light. Marginally better penetration than visible light, and significantly easier to generate. Lots of cooking uses infrared light.
3. Radio waves. The radio spectrum is huge. Really low frequencies are hard to generate but penetrate well, really high frequencies are hard(er) to generate and penetrate poorly. Microwaves use a middle of the road frequency that is easy to generate with a magnetron and penetrates moderately well.
Microwaves have the edge of penetration over conventional infrared/convective cooking, so they are used for “fast” cooking.
If the light *has* to be nonionizing, then we’re essentially stuck with:
1. Visible light. This does not penetrate super well into food, is hard to generate in necessary quantities. It would also be blinding if you *did*. This would just sear the surface if you tried to cook too fast with it.
2. Infrared light. Marginally better penetration than visible light, and significantly easier to generate. Lots of cooking uses infrared light.
3. Radio waves. The radio spectrum is huge. Really low frequencies are hard to generate but penetrate well, really high frequencies are hard(er) to generate and penetrate poorly. Microwaves use a middle of the road frequency that is easy to generate with a magnetron and penetrates moderately well.
Microwaves have the edge of penetration over conventional infrared/convective cooking, so they are used for “fast” cooking.
Water molecules vibrate at a frequency that is resonant at microwave frequencies. I’m not sure if they vibrate at microwaves’ fundamental frequency ot a harmonic. But the point is that molecules react more to microwaves because the energy transfer between the radio waves and water molecules is more efficient at resonance.
Water molecules vibrate at a frequency that is resonant at microwave frequencies. I’m not sure if they vibrate at microwaves’ fundamental frequency ot a harmonic. But the point is that molecules react more to microwaves because the energy transfer between the radio waves and water molecules is more efficient at resonance.
If the light *has* to be nonionizing, then we’re essentially stuck with:
1. Visible light. This does not penetrate super well into food, is hard to generate in necessary quantities. It would also be blinding if you *did*. This would just sear the surface if you tried to cook too fast with it.
2. Infrared light. Marginally better penetration than visible light, and significantly easier to generate. Lots of cooking uses infrared light.
3. Radio waves. The radio spectrum is huge. Really low frequencies are hard to generate but penetrate well, really high frequencies are hard(er) to generate and penetrate poorly. Microwaves use a middle of the road frequency that is easy to generate with a magnetron and penetrates moderately well.
Microwaves have the edge of penetration over conventional infrared/convective cooking, so they are used for “fast” cooking.
Water molecules vibrate at a frequency that is resonant at microwave frequencies. I’m not sure if they vibrate at microwaves’ fundamental frequency ot a harmonic. But the point is that molecules react more to microwaves because the energy transfer between the radio waves and water molecules is more efficient at resonance.
Resonance. (I hope you know resonance, if not, check that first)
You shoot a wave that resonate with water molecules frequency, hence they move, hence become hot. And it’s a specific frequency, it won’t heat other molecules. Completely dry food won’t heat up.
Each electromagnetic frequency tend to interact with specific matter, and ignore or bounce on other. Like concrete is transparent to radio but reflects light, both are electromagnetic waves, but have different length.
The magic of the microwave is that the wave can go through things but not water, so it gets into the food, deep, and heats it inside.
You can heat food with light but it will interact with all the food particles, heating only the surface, will fail to penetrate.
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