[Corvettaholic]

So I was thinking about my microwave oven again (just got back a couple days ago from playing army) and I remembered that microwave ovens work because they cause water molecules to vibrate thereby generating heat. I don't think the frequency is dead on, but its something like 2.4ghz. Now how do I find out resonance frequencies for other stuff? I want to make other objects vibrate to generate heat, such as chairs or golf balls or bones.

Also, can microwaves be measured in decibals (even though we can't hear them normally) or are they only measured with wattage?

[lemonoman]

Well chairs are made of wood.  Wood is cells, and cells are what, 70 or 90% water?  I recommend putting a piece of wood in a microwave to see if it heats up...

My other thought is...do the water molecules that rotate have to be free (ie in liquid or solid phase)?  Can Ice be melted lightning-fast by microwave?  For some reason I think the answer is no...because the molecules can't rotate (and hence absorb energy) when they're in the crystal structure...Anyways, in that case, you can't heat up crystal structures just by finding the resonance frequencies of the molecules inside...something to think about...

And no, I don't think microwaves can't be measured in decibels...Decibels are meant for sound waves which are Longitudinal in nature...microwaves are electromagnetic radiation...

[Qazzian]

well, if you look at the formula for decibels, you have B = 10 log (I/Io) where I is the intensity in Watt/m^2 (power over area). So according to the units, unless I'm missing something, yes, you could.

And the molecules don't rotate, they vibrate. Ice DOES melt faster, that's why there's the "Defrost" function on microwaves :p

To get other things to resonate, I'm guessing you'd just need to find a wavelength that would work with the bonds in the that substance. So bone, find the structure of marrow (of course, if you're going after bone IN a person, using the frequecy for water would be much more useful. But I'm not suggesting anything )

[Borek]

And the molecules don't rotate

Yes they do. They vibrate, rotate and move.

[Corvettaholic]

So I'm going to sum up all the ways a water molecule moves as 'jiggle'. Since 2.4ghz will make water 'jiggle', heat is produced. So lets pretend bone 'jiggles' at 3ghz (probably not true). Then if I had a magnetron tuned to 3ghz and blasted a chunk of bone it would behave the same as if I put a cup of water in my microwave oven, as in makes heat and if there's enough heat it could combust or something.

Is there a way to figure out what frequency I need for any particular material, like equation or something? It'd be neat to vibrate iron...

Oh, and sound is electromagnetic radiation too isn't it? I understand if you vibrate a voice coil in a speaker it pushes air at whatever frequency and our ears can pick up the vibrating air and translate that into what we hear in our heads. So what if you had an antenna that transmits in the same frequency as a home audio system? But air isn't being pushed around, so the answer would be you couldn't hear it?

While I'm on a roll here, I got a question about amplification too! If my previous paragraph is correct, then I need some fancy pants way to amplify a sound wave after it has left the speaker. If a sound wave hits water, it distorts right? If its in an enclosed room, it'll echo. What if I tried to shoot a sound wave through a big ol piece of plywood with a hole in the middle? How would the hole in the middle effect the sound wave?

[Qazzian]

Yes they do. They vibrate, rotate and move.

I was under the impression the microwave worked by increasing the vibration. I'm not saying the don't rotate AT ALL, I mean in regards to how microwaves work.

[Corvettaholic]

Just thought of something... is there such a thing as a waveguide for sound waves? I know about waveguides for microwaves, but thats electromagnetic as opposed to pressure waves...

Oh, and how does a megaphone make your voice sound louder? Wouldn't it be neat to take the output from a megaphone and channel it back into the input? Too bad thermodynamics exists   So much for perpetual motion. I just want enough decibals to blow down a door or something, and I want it aim-able...