Can we use any electromagnetic wave (eg: radio wave, light waves etc) for cooking food?

Question

A microwave oven cooks food using microwaves. The oscillating electric field in microwaves rotates the water molecules in our food. As all waves have oscillating electric fields, my question is why we don't use other waves (radio, visible, gamma etc) in oven.

Answer 1

Sort of. The question is not whether they can be used, but whether they can be used efficiently.

It sounds a bit strange to talk about "antenna matching" when one of the antennae is a lasagne, but that's what's going on. The target will absorb EM radiation of different wavelengths with different levels of efficiency. Other wavelengths will be reflected, or transmitted straight through. The wavelength used by microwaves is chosen because water absorbs it particularly well.

Microwaves also penetrate reasonably well into the food. Visible and IR radiation can be used: IR ovens are common in industrial processes, and an electric grill is effectively transmitting most of its heat through infrared radiation. But they don't penetrate and are instead used to heat the outer surface of food, causing browning rather than cooking through.

Answer 2

You can cook food with any wavelength of EM radiation that is sufficiently absorbed by the food. Of course if you have a sufficiently strong source, you could even heat food with very penetrating radiation like x-rays.

Ionizing radiation such as UV and x-rays will destroy proteins and vitamins though.

Very low frequency radiation is also very penetrating and cant be focused well, so you either need a very large meal or have to accept heating the surroundings.

In practise the dominant forms are infrared (e.g. toasters) and microwave ovens tuned to the absorption frequency of water molecules.

Answer 3

It's amazing that the technology is quite consolidated and dates back to the end of the World War II (https://en.wikipedia.org/wiki/Microwave_oven). A magnetron used for radars straightforwardly reused for something to last more that WW-II: desire for peace? big market move ensuring a long-lasting production after the boom for war reason?

The typical frequency is 2.45 GHz, but applications at 915 MHz exist for industrial use. Then you can heat metals e.g. for sintering and alloy processing mixing the effect with eddy current, so going to lower frequencies.

An interesting discussion already took place in SE: https://physics.stackexchange.com/questions/172790/why-do-we-use-microwaves-in-microwave-oven Another paper that may be worth a look is: http://www.sfu.ca/phys/346/121/resources/physics_of_microwave_ovens.pdf

One might ask why right 2.45 GHz: in reality it is not sharp and we may use other frequencies there about, but it's a matter of standardization. These frequencies are quite efficient in getting the vibration by repetitive reorientation of the water molecules. Looking at http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/mwoven.html "the detailed modeling of water heating described in Chaplin ["Water Structure and Science" by Martin Chaplin] suggests that the major effect of the microwaves is from work done on the hydrogens rather than invested in the reorientation of the molecular dipoles of the water molecules."

I confess that I don't like so much the microwave oven, because it's ok to defrost but cooking, unfortunately, is a different theme. Things come out too soft for me. I'm Italian so a bit "susceptible" on such topic. Of course I myself use other wavelengths, such as solar radiation when putting frozen meat on the widow sill (dangerous process, too exposed: cats, crows, ...).

Answer 4

You certainly can cook food with other wavelength like solar oven.

Actually most kitchen oven use heating elements that produces infra-red (light), which is the primary heating factor.

The wavelength also has to be such that it can produce heat on organic materials, radiowave, which are long waves mostly goes through.

Microwave, of shorter wavelength, will penetrate in the food and heat it.

Light wave, very short, will barely penetrate and will mostly heat at the surface.

Answer 5

The basic reason is that the water molecules in the food resonate at the 2.45 GHz frequency that the microwave oven uses. This is what allows the microwaves to couple to the water molecules, causing them to vibrate and thus heat up the food.

It's also the reason why a microwave over doesn't affect, very much, objects that do not have water in them (metal objects excepted), and also the reason why frequencies other than 2.45 GHz do not affect food products, at least very much.