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Thread: Do any substances radiate at only one frequency when hot?

  1. #1 Do any substances radiate at only one frequency when hot? 
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    I'm just curious. I'm not too well studied in this area. I know tungsten, in light bulbs, radiates light when it gets hot, but this is pretty much white light, at a wide range of frequencies.

    Are there any substances that only radiate at one frequency, or a narrow band, or just a few discreet frequencies?


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  3. #2  
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    I don't think so. Hot things radiate light because of black body radiation. The light radiated is actually a continous spectrum which covers basically the entire light spectrum. However, certainly the majority of light can be concentrated on very specific colors. This is the basis for things like colored fireworks and UV lamps.


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    I think every object has the same spectrum of radiation caused by temperature. The difference in colour originates in other sources (absorption/reflection/fluorescence; mostly something to do with the energy levels of outer electrons in atoms/molecules). Also the colour that results from burning certain substances (such as in fireworks) depends more on the substance than on the temperature.
    This is why we like the light of light bulbs more than the light of a TL lamp: it has a similar spectrum to the sun, while a TL lamp concentrates a large part of its emitted light in some spikes, making colours look different. It's also why a TL lamp consumes a lot less energy: its light is concentrated in the visible spectrum.
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  5. #4  
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    yes they are called LASERS. Special case though.
    In normal situations the answere is no.
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    Quote Originally Posted by Bender
    I think every object has the same spectrum of radiation caused by temperature. The difference in colour originates in other sources (absorption/reflection/fluorescence; mostly something to do with the energy levels of outer electrons in atoms/molecules). Also the colour that results from burning certain substances (such as in fireworks) depends more on the substance than on the temperature.
    Oh yes, I hadn't thought about substances' emission spectrum. How does black body radiation and emission spectrum jive?
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    I think you can superimpose them. Each element/molecule can also cause absorption lines in the spectrum, I think, which can be seen in the spectrum of stars.
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  8. #7  
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    Quote Originally Posted by fizzlooney
    yes they are called LASERS. Special case though.
    In normal situations the answere is no.
    What is used as the source of light for lasers? Is it neon, or some other chemical like that? Is the uniformity of color a property of the chemical/temperature, or the result of some additional process?
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    Quote Originally Posted by kojax
    Quote Originally Posted by fizzlooney
    yes they are called LASERS. Special case though.
    In normal situations the answere is no.
    What is used as the source of light for lasers? Is it neon, or some other chemical like that? Is the uniformity of color a property of the chemical/temperature, or the result of some additional process?
    Its not the light source that fixes the frequency, it is the crystalline substance the light is forced through.
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    No, there are soild, liquid and gas lasers,ever see a a crystayline gas or liquid.
    Lasers work by stimulated emission of photons , not any crystal effect .
    you can look it up on " how things work.com" Bye enough of this one too.
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  11. #10  
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    Still, it's the medium the light passes through, not the original stimulus light that sets the color.
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    So, does the medium block the undesired frequencies, or convert them? Or does it absorb and re-emit them?
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    Its the energy difference of the electron transitionthat determines the frequency of the photon.
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  14. #13  
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    Quote Originally Posted by kojax
    So, does the medium block the undesired frequencies, or convert them? Or does it absorb and re-emit them?
    Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. That stimulated emission is what you're asking about. What happens is the original light stimulates the medium to release more light, which in turn causes it to release more light, etc. Since all the light released (not including the original pulse) is the same frequency and headed in the same direction, you get a laser.
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    Quote Originally Posted by fizzlooney
    No, there are soild, liquid and gas lasers,ever see a a crystayline gas or liquid.
    Lasers work by stimulated emission of photons , not any crystal effect .
    you can look it up on " how things work.com" Bye enough of this one too.
    First of all, yes, there are crystal liquids, hence LCD screens and displays (Liquid Crystal), but either way that medium is put into a CRYSTAL TUBE, hence RUBY LASERS. Its what FILTERS THE SPECTRUM OF LIGHT(frequency). Not to mention SOLID STATE LASERS use a crystalline semiconducting medium. So try not to correct people when you have no idea what you're talking about. The same method of energy amplification is used in thermoacoustics. Heat actually magnifies sound energy through a compressed gas.
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  16. #15  
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    So, what are the losses like?

    Is a laser a very efficient heat-to-light transducer? (Or electricity-to-light?)
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    Quote Originally Posted by kojax
    So, what are the losses like?

    Is a laser a very efficient heat-to-light transducer? (Or electricity-to-light?)
    Depends on the laser. If it is in the visual spectrum, I think it's quite efficient, but you only have one wavelength of light, so you won't see any colours. In e.g. a CO2 laser, where the wavelength falls in the infrared, its efficiency is obviously very close to 0.
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    Quote Originally Posted by kojax
    So, what are the losses like?
    Most lasers are 30% or less efficient (meaning that your laser will absorb twice as much heat as its able to deposit into a target, which is why powerful lasers usually need cooling systems). I believe there have been some laboratory prototypes of high efficiency solid state lasers demonstrated that have efficiencies greater than 50%, but I don't think those are actually for sale yet. So far as I know, there's no theoretical reason why solid state lasers couldn't be made much more efficient, we just haven't figured out how to do it yet.

    The big exception to this is free electron lasers, which I believe can be made close to 100% efficient, but these are big gadgets the size of a smaller car (and often much bigger). They work by accelerating electrons to a high speed and then making them oscillate back and forth with magnetic fields, causing them to emit photons, which is pretty different from how other lasers work.
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  19. #18  
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    Quote Originally Posted by yelram
    Quote Originally Posted by fizzlooney
    No, there are soild, liquid and gas lasers,ever see a a crystayline gas or liquid.
    Lasers work by stimulated emission of photons , not any crystal effect .
    you can look it up on " how things work.com" Bye enough of this one too.
    First of all, yes, there are crystal liquids, hence LCD screens and displays (Liquid Crystal), but either way that medium is put into a CRYSTAL TUBE, hence RUBY LASERS. Its what FILTERS THE SPECTRUM OF LIGHT(frequency). Not to mention SOLID STATE LASERS use a crystalline semiconducting medium. So try not to correct people when you have no idea what you're talking about. The same method of energy amplification is used in thermoacoustics. Heat actually magnifies sound energy through a compressed gas.
    Gain media for lasers don't have to be crystals, and they aren't filters, though some might be either or both. (Also, try this link.)
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    GFY
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    Quote Originally Posted by MagiMaster
    Quote Originally Posted by yelram
    Quote Originally Posted by fizzlooney
    No, there are soild, liquid and gas lasers,ever see a a crystayline gas or liquid.
    Lasers work by stimulated emission of photons , not any crystal effect .
    you can look it up on " how things work.com" Bye enough of this one too.
    First of all, yes, there are crystal liquids, hence LCD screens and displays (Liquid Crystal), but either way that medium is put into a CRYSTAL TUBE, hence RUBY LASERS. Its what FILTERS THE SPECTRUM OF LIGHT(frequency). Not to mention SOLID STATE LASERS use a crystalline semiconducting medium. So try not to correct people when you have no idea what you're talking about. The same method of energy amplification is used in thermoacoustics. Heat actually magnifies sound energy through a compressed gas.
    Gain media for lasers don't have to be crystals, and they aren't filters, though some might be either or both. (Also, try this link.)
    All lasing mediums attempt to mimic a crystalline state. The ability to repeat the phenomenon less efficiently with a different medium does not discount the true cause of this effect, it is the organized spacing of the atoms that allows photons to be absorbed and passed on easily, and maintain their coherence. It is the spacing, and organization of the medium that determines the frequency. The most efficient Gas laser is produced using CO2, a crystalline compound. It is the shape of these compounds that allows for a specific spectrum of light to be amplified. ALL SOLID STATE LASERS USE CRYSTALLINE MEDIUMS.
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  22. #21  
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    YOU GUYS ARE NUTS!
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  23. #22  
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    Quote Originally Posted by yelram
    Quote Originally Posted by MagiMaster
    Gain media for lasers don't have to be crystals, and they aren't filters, though some might be either or both. (Also, try this link.)
    All lasing mediums attempt to mimic a crystalline state. The ability to repeat the phenomenon less efficiently with a different medium does not discount the true cause of this effect, it is the organized spacing of the atoms that allows photons to be absorbed and passed on easily, and maintain their coherence. It is the spacing, and organization of the medium that determines the frequency. The most efficient Gas laser is produced using CO2, a crystalline compound. It is the shape of these compounds that allows for a specific spectrum of light to be amplified. ALL SOLID STATE LASERS USE CRYSTALLINE MEDIUMS.
    Dye lasers? Glass lasers?

    Anyway, can you provide some reference for your claims? Nothing I can find on lasers says that a crystalline state has any effect on anything.
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  24. #23  
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    Dyes and Gases are not solid states of matter, so I'm guessing a laser that uses them doesn't count as a "solid state laser". But then we're just talking about names.

    I'm getting the impression that crystal based lasers are usually the most effective. (Sort of like how crystal based oscillators are usually considered among the most reliable..... short of an atomic clock, anyway).
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  25. #24  
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    Quote Originally Posted by yelram
    All lasing mediums attempt to mimic a crystalline state. The ability to repeat the phenomenon less efficiently with a different medium does not discount the true cause of this effect, it is the organized spacing of the atoms that allows photons to be absorbed and passed on easily, and maintain their coherence. It is the spacing, and organization of the medium that determines the frequency. The most efficient Gas laser is produced using CO2, a crystalline compound. It is the shape of these compounds that allows for a specific spectrum of light to be amplified.
    Why do people always insist on confidently pretending that they know what the hell they're talking about, even when they obviously don't? I don't really feel like writing an introduction to lasers and solid state physics, which is pretty much what would be necessary to explain everything wrong in this post, but most of the stuff here is nonsensical bullshit.
    ALL SOLID STATE LASERS USE CRYSTALLINE MEDIUMS.
    Except, of course, all the solid state glass lasers...
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  26. #25  
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    Quote Originally Posted by kojax
    Dyes and Gases are not solid states of matter, so I'm guessing a laser that uses them doesn't count as a "solid state laser". But then we're just talking about names.

    I'm getting the impression that crystal based lasers are usually the most effective. (Sort of like how crystal based oscillators are usually considered among the most reliable..... short of an atomic clock, anyway).
    Just to point out, but I said glass not gas. (Dye lasers are liquid, but he was also arguing that liquids would have to be something like liquid crystal.)
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by yelram
    All lasing mediums attempt to mimic a crystalline state. The ability to repeat the phenomenon less efficiently with a different medium does not discount the true cause of this effect, it is the organized spacing of the atoms that allows photons to be absorbed and passed on easily, and maintain their coherence. It is the spacing, and organization of the medium that determines the frequency. The most efficient Gas laser is produced using CO2, a crystalline compound. It is the shape of these compounds that allows for a specific spectrum of light to be amplified.
    Why do people always insist on confidently pretending that they know what the hell they're talking about, even when they obviously don't? I don't really feel like writing an introduction to lasers and solid state physics, which is pretty much what would be necessary to explain everything wrong in this post, but most of the stuff here is nonsensical bullshit.
    ALL SOLID STATE LASERS USE CRYSTALLINE MEDIUMS.
    Except, of course, all the solid state glass lasers...
    So lets see a list of glass lasers here, first we have the most popular neodymium doped glass, so whats it doped with? Neodymium oxide, and what exactly is that?

    "Neodymium(III) oxide or neodymium sesquioxide is the chemical compound composed of neodymium and oxygen with the formula Nd2O3. It forms hygroscopic blue hexagonal crystals[1]. The rare earth mixture didymium, previously believed to be an element, partially consists of neodymium(III) oxide[3]."

    Crystals

    Then Ytterbium.
    "Ytterbium has three allotropes which are called alpha, beta and gamma and whose transformation points are at −13 C and 795 C. The beta form exists at room temperature and has a face-centered crystal structure while the high-temperature gamma form has a body-centered crystal structure."

    Crystals
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  28. #27  
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    Quote Originally Posted by yelram
    So lets see a list of glass lasers here, first we have the most popular neodymium doped glass, so whats it doped with? Neodymium oxide, and what exactly is that?

    "Neodymium(III) oxide or neodymium sesquioxide is the chemical compound composed of neodymium and oxygen with the formula Nd2O3. It forms hygroscopic blue hexagonal crystals[1]. The rare earth mixture didymium, previously believed to be an element, partially consists of neodymium(III) oxide[3]."

    Crystals

    Then Ytterbium.
    "Ytterbium has three allotropes which are called alpha, beta and gamma and whose transformation points are at −13 C and 795 C. The beta form exists at room temperature and has a face-centered crystal structure while the high-temperature gamma form has a body-centered crystal structure."

    Crystals
    Just because neodymium and ytterbium can be crystalline, doesn't mean that they are still crystalline when they're spread into a glass. Do you even know what "glass" means? When you dope glass with neodymium to make a lasing medium, the neodymium ions spread out into the glass and become amorphous.
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  29. #28  
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    Holy shiiiiit , the answer to the original question is NO!
    Sorry I even mentioned lasers, brought out all the screwballs.
    At least go look up how lasers work before putting out all the BS!
    KILL THIS THREAD AND PUT US OUT OF THIS MISERY!
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  30. #29  
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by yelram
    All lasing mediums attempt to mimic a crystalline state. The ability to repeat the phenomenon less efficiently with a different medium does not discount the true cause of this effect, it is the organized spacing of the atoms that allows photons to be absorbed and passed on easily, and maintain their coherence. It is the spacing, and organization of the medium that determines the frequency. The most efficient Gas laser is produced using CO2, a crystalline compound. It is the shape of these compounds that allows for a specific spectrum of light to be amplified.
    Why do people always insist on confidently pretending that they know what the hell they're talking about, even when they obviously don't? I don't really feel like writing an introduction to lasers and solid state physics, which is pretty much what would be necessary to explain everything wrong in this post, but most of the stuff here is nonsensical bullshit.
    It would actually be cool if you did.

    ALL SOLID STATE LASERS USE CRYSTALLINE MEDIUMS.
    Except, of course, all the solid state glass lasers...
    Well... technically..... glass at room temperature is in a liquid state, not a solid one. But I'm guessing that glass lasers are still considered solid state lasers.
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  31. #30  
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    Glass is not technically liquid; rather, it is an amorphous solid.

    What appear to be liquid properties are actually plastic deformation due to stress, i.e. gravity.

    However, whether glass is liquid or solid at certain temperatures is hard to say, as there is a continuous scale rather than a specific melting point.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  32. #31 Re: Do any substances radiate at only one frequency when hot 
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    Quote Originally Posted by kojax
    I'm just curious. I'm not too well studied in this area. I know tungsten, in light bulbs, radiates light when it gets hot, but this is pretty much white light, at a wide range of frequencies.

    Are there any substances that only radiate at one frequency, or a narrow band, or just a few discreet frequencies?
    I assume by substances you are referring to the periodic table. In their rest
    states the answer is 'no'. Here is a link to the NIST database.
    http://physics.nist.gov/PhysRefData/ASD/index.html

    But atomic spectral emissions & absorptions are dependent on a number of factors,
    pressure & temp for two. Under certain conditions a number of atoms can be made
    to lase, that is emit (or absorb) at a monochromatic wavelength, which others have
    already noted here. The case of molecules is different. Spectral traits of molecules tend to depend on the rotational states of the molecules vs. electron states and motions in atoms. (CN is one common molecular emission in comets, for example)

    There is a growing body of information about the various aspects of spectroscopy
    on the web - surprisingly more than just 5 years ago. Just do Google searches
    using /spectra/ or /spectroscopy/ and you will call up a lot information including
    many tutorials (some very good).

    As you file through the NIST lists of spectral emissions for period elements
    you will notice many wavelength emissions for a given element say H (hydrogen),
    from th extreme end of the IR clear down deep into the UV ... the combined total
    of these emissions of course conforms to a given black body temp Planck curve
    for that element, and is calculable. However, not each emission is equally strong
    as it relates to particular electron transitions between particular electron shells,
    or states. Thus in the case of Hydrogen, for example, we have several strong
    groups of emission (or energy-gradient sets) the strongest of which in the visual range is the Balmer Series. This consists of Halpha (6563A), Hbeta (4861A in the
    blue), Hgamma (4340) ... and the like until the next energy series known at the
    Lyman series.

    And yes (people always ask) people can do spectroscopy at the amateur level
    with telescopes. Its fun! You might also be interested in that. There are several
    amateur spectroscopy Yahoo Tech groups which you could join, if you like.

    I hope this answers a few questions?




    series
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  33. #32 Re: Do any substances radiate at only one frequency when hot 
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    Quote Originally Posted by Anonymous

    Under certain conditions a number of atoms can be made
    to lase, that is emit (or absorb) at a monochromatic wavelength, which others have
    already noted here.

    So, are you saying that, some elements will emit just one frequency if you have them at the right temperature and pressure?

    I hope this answers a few questions?
    Yeah, it does. Thanks. :-)
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