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Thermometer measures the amount of infra-red radiation only

  1. Aug 24, 2005 #1
    A thermometer measures the amount of infra-red radiation only, right?
    so, if equivalent amount of visible light is illustrated on the bulb, the temperature for the infra-red rises much more, doesn't it?
  2. jcsd
  3. Aug 25, 2005 #2


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    That doesn't make sense to me. What do you mean by "temperature for the infra-red"? "Rises much more" than what?
  4. Aug 26, 2005 #3
    Matter expands or contracts only when there's change of the infra-red radiation level but not other electromagnetic wave, doesn't it?
  5. Aug 26, 2005 #4
    If you are talking about ordinary Thermometers , they work on the property of mercury expansion on increase in temperature , the rise of mercury in tube gives us the degree celsius . Apart from that I cannot decipher what you mean in your question.

  6. Aug 26, 2005 #5

    jim mcnamara

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    Mercury thermometers show how much a mecury column expands as it gains heat energy. Or contracts as it loses heat energy.

    Any flavor of light that can be absorbed by an object adds energy to the object it "shines" on. Like a car with closed windows left in a parking lot heating with exposure to sun light.

    Infa-red is light that has a wavelength a little longer than light that is visible to humans. Some animals can perceive some infa-red light with their eyes or with special organs like Jacobsen's organ in pit vipers. Humans cannot see infa-red, but we can perceive it as "heat" when it is hitting our skin. I think this is your confusion - you feel infa-red as heat, so you assume, incorrectly, that all heat is infa-red light.
  7. Aug 27, 2005 #6


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    The heating effect of electromagnetic waves decreases with decrease in wavelength and the chemical effect increases with wavelength. Thus the electromagnetic waves of all wavelengths have thermal effect, may be more or less.
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