Lightwave Oven: Why We Heat Food With Microwave

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Microwave ovens heat food effectively because microwaves operate at 2.45 GHz, which causes polar molecules, primarily water, to oscillate rapidly through dielectric heating. This process generates heat by making molecules bump into each other, unlike visible light, which heats only surfaces due to its limited penetration depth. While light can also generate heat, it does not penetrate food deeply, making it less effective for cooking. The choice of 2.45 GHz was largely due to it being an unused frequency at the time of microwave oven development, not because of any unique heating properties. Understanding these principles clarifies why microwaves are preferred for heating food over visible light.
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why we can heat food with microwave and not light wave (the light we can see) fast?
 
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I'm not sure that I'm using the proper terminology here, but essentially microwaves are attuned to the resonance frequency of water molecules, and so make them oscillate rapidly. That's what causes the heat. It's more complicated than that, but someone else can help clear it up for you.
 
Not quite. Liquid water doesn't have a well-defined resonance and microwave ovens at 2.45 GHz operate well below the peak resonance of water vapor at around 30 GHz. Instead, microwaves heat by a process called dielectric heating, in which polar molecules (in foods, mainly water but also fats and sugars) are tugged back and forth extremely rapidly causing them to bump and slam into neighboring molecules, imparting kinetic energy--heat. Light can heat too--you never burned ants with a magnifying lens as a kid? The problem with light is it doesn't penetrate very far before being entirely absorbed so only the surface gets heated; microwaves can penetrate more deeply, allowing for more thorough cooking. Why 2.45 GHz? At the time these ovens were being invented, nothing really used this band: communications used much lower frequencies and radio astronomy used higher ones so a frequency was chosen that was relatively unused. There's nothing special about it in terms of heating capability. Industrial microwaves used for things like curing glues typically use 915 MHz.
 
thanks
 
Thanks, Negitron. I knew that I didn't have it quite right, but wasn't sure why. :redface:
 
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