CPL.Luke Posted August 16, 2005 Share Posted August 16, 2005 what frequency of microwaves would be best absorbed in hydrogen? Any textbook with more information like this would also be apreciated also does this change with different isotopes of hydrogen? Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2005 Share Posted August 16, 2005 what frequency of microwaves would be best absorbed in hydrogen? Any textbook with more information like this would also be apreciated also does this change with different isotopes of hydrogen? 21 cm' date=' or 1420 MHz[/url']. Very imprtant in radioastronomy. There should be an isotope shift, but don't know how big it is. Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 16, 2005 Author Share Posted August 16, 2005 thankyou, by any chance is there a text book specifically on EM waves, and there interactions with matter, also what level of math would you say is required in order to understand it? Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2005 Share Posted August 16, 2005 Three that I have are The Quantum Theory of Light Rodney Loudon The Quantum Theory of Radiation W. Heitler Applied Laser Spectroscopy W. Demtroder all are upper level undergraduate-to-graduate level physics. You need to have learned quantum mechanics. Math requirement is calculus, basically. Maybe differential equations. Link to comment Share on other sites More sharing options...
H2SO4 Posted August 16, 2005 Share Posted August 16, 2005 just curious, why do you need to know what frequence of microwave radiation H absorbs best? Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 16, 2005 Author Share Posted August 16, 2005 its for my intel science project this year, some of it has to do with fusion (nothing I intend on trying) Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 16, 2005 Author Share Posted August 16, 2005 also, if waves destructively interfere with eachother in one area does that use up any energy? Link to comment Share on other sites More sharing options...
Klaynos Posted August 16, 2005 Share Posted August 16, 2005 also, if waves destructively interfere with eachother in one area does that use up any energy? No they just cancel each other out effectively, there is no energy used in doing this... Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 16, 2005 Author Share Posted August 16, 2005 good thats what I thought. very important to what I'm working on as well Link to comment Share on other sites More sharing options...
MetaFrizzics Posted August 17, 2005 Share Posted August 17, 2005 also, if waves destructively interfere with eachother in one area does that use up any energy?I think you have to qualify this:There are scenarios in which waves can be completely out of sync (180o) and still transmit energy to a target (made of more than one primitive particle). For instance you can beam waves at an object from opposite sides and heat it up or compress it, performing work and transferring energy. As a static analogy, consider the huge difference between a weight hanging freely on a string, and the same weight also held in place horizontally by elastics or springs. The behaviour of the weight will be different, and new reservoirs for energy storage and exchange will have been created. Similarly, the EM field in Maxwell's classical EM theory acts as a 'reservoir' and transfer medium of energy, preventing simple cancelling of field potentials. Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 18, 2005 Author Share Posted August 18, 2005 wait, just for clarity, your saying that even if two beams of em radiation are 180 degrees out of sinc and are fired facing toward each other, if there is a mass in the way, the mass will absorb them before they can interfere? Link to comment Share on other sites More sharing options...
MetaFrizzics Posted August 18, 2005 Share Posted August 18, 2005 Yes. I'm saying there is a strong chance that waves will interact with the mass at various levels of penetration with resultant exchange of energy and work done as heat before the waves carried by the field can cancel. In fact I would predict a wave-like probability pattern in the absorption and also re-emission of EM radiation based upon a QM-type distribution in space along the direction of transmission. Keep in mind that waves from different sources can never completely cancel everywhere, since they are spherical expansions, and will always exhibit Moire' patterns of reinforcement and cancellation even in perfectly isotropic mediums. Link to comment Share on other sites More sharing options...
YT2095 Posted August 18, 2005 Share Posted August 18, 2005 21 cm' date=' or 1420 MHz[/url']. Very imprtant in radioastronomy. There should be an isotope shift, but don't know how big it is. My radio will do that frequency easily and in any mode, what sort of antenna and mode would I need to do anything interesting with? I assume I`de need some sort of dish? Link to comment Share on other sites More sharing options...
Locrian Posted August 18, 2005 Share Posted August 18, 2005 Swansont answered your question correctly. However, if you are considering using microwaves to generate a plasma, choosing that frequency may not be your best option. The choice of frequency actually more often depends on your cavity size and resonance condition and what frequency power supplies are available in. I've never seen anyone selling a 1420mhz microwave generator with any significant power for a reasonable price. We use a 915mhz to generate plasma here, and 2450 works fine too. Both have low reflected power under a reasonable load. So you have some room to work. As for understanding E&M, why not start with Griffiths Electrodynamics textbook? Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 18, 2005 Author Share Posted August 18, 2005 wouldn't it be possible though to create a chamber in which the 1420 mhz system works just as well or better than the 915 or 2450? Link to comment Share on other sites More sharing options...
Locrian Posted August 18, 2005 Share Posted August 18, 2005 Certainly as good as. I'm not sure in what way it would be better. What are your goals? Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 18, 2005 Author Share Posted August 18, 2005 I'm trying to confine the plasma through the use of microwaves Link to comment Share on other sites More sharing options...
YT2095 Posted August 18, 2005 Share Posted August 18, 2005 I'm trying to confine the plasma through the use of microwaves I may be speaking out of turn here (it`s been one of those days) but wouldn`t a magnetic feild be a better method of confinement? Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 18, 2005 Author Share Posted August 18, 2005 eh I'm not sure, for the kind of project that this just proving that its possible would be good enough (doesn't really matter if its more effective) but I would say that the advantage of being able to carefully construct different shapes in which the plasma is contained might be of use, also in the case where superconducting magnets aren't used the microwaves might prove more efficient, and finally if you contain the plasma using microwaves you can combine both the heating and the containment mechanisms into 1 system. This could make it a bit more efficient Link to comment Share on other sites More sharing options...
Locrian Posted August 19, 2005 Share Posted August 19, 2005 I'm trying to confine the plasma through the use of microwaves Well that's relatively easy. In a well constructed chamber with a good power source the size of your plasma will be inversely proportional to the pressure and directly proportional to the power. We use these facts to control the size of our plasma ball and the temperature of our substrate daily. However, I noticed you were considering this for fusion power. I believe there are technical barriers to this, probably not the least of which is getting a powerful enough microwave source. As an experimentalist I can give you lots of general knowledge about what's its like working with hydrogen & methane plasmas, but I know very little about applying this to fusion power. Link to comment Share on other sites More sharing options...
CPL.Luke Posted August 19, 2005 Author Share Posted August 19, 2005 really?, does your lab have a website? I would love to read through it Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now