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Infrared Emission of A Person

  1. Dec 6, 2008 #1
    In order to detect SARS, airport officials would use infrared cameras to find potential carriers. A healthy individual would be detected to emit 100microwatts at 37C body temperature, what would a sick individual at 40C body temperature emit? With this answer, what is the difference in emission of a sick individual and a healthy one?

    2. Relevant equations

    Radiation out = (5.67*10^-8)(e)(A)(T)^4

    Where e ~ 1.

    3. The attempt at a solution

    0.0001W = (5.67*10^-8)(1)(A)(37)^4

    A = 0.000941044249m^2

    X W = (5.67*10^-8)(1)(0.000941044249)(40)^4

    X W = 0.000136594455

    0.000136594455-0.0001 = 0.00003659W = 36.59 microwatts

    However, this is apparently the wrong answer. Am I going at the problem in a completely wrong direction?

    Thanks alot for any help.
  2. jcsd
  3. Dec 6, 2008 #2


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    Homework Helper

    Welcome to PF.

    For one thing the Stephan-Boltzmann equation implies the use of degrees °K not °C.

    So your temps should be 310° and 313°K

    All other things being equal then

    X/100 = (313)4/(310)4

    should yield an answer in microwatts shouldn't it?
  4. Dec 6, 2008 #3
    Wow that was stupid. Thank you very much for the correction..yes that produces a correct answer.
  5. Dec 6, 2008 #4


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    Homework Helper

    Easy to overlook.

    Yet amazingly think how smart nature is to get it right every time.

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