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Question on spectral lines

  1. Oct 7, 2013 #1
    This lady who takes our class, she set this question in one of our papers:

    'The wavelengths of the dark lines are exactly the same as those of bright lines in the absorption spectrum.' - True or false?

    I answered true. Have I been wrong?
     
  2. jcsd
  3. Oct 7, 2013 #2

    Simon Bridge

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    When she asks for the wavelength for a bright fringe (line), what is she referring to?
     
  4. Oct 7, 2013 #3
    I asked her the same question during the exam, and she replied that I have to figure that out by myself.

    I answered true out of a pre-emptive notion that that bright lines implicitly refer to an emission spectrum.

    The lady marked my answer wrong, and explained that the answer should be false because there are no bright lines in an absorption spectrum.

    What are your thoughts?
     
  5. Oct 7, 2013 #4

    Simon Bridge

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    The wavelengths of the dark lines are exactly the same as those of bright lines in the absorption spectrum.

    Did you perhaps read that as meaning:
    "The wavelengths of the dark lines in the absorption spectrum are exactly the same as those of bright lines in the corresponding emmission spectrum."

    But it does not actually say that - the grammar of the original question related bright lines to the absorption spectrum.
    If that is the only information - then your reading was in error.

    You want me to say you were right and your teacher wrong? - I don't have enough information.
    I think your answer is better as a long answer, because it needs the explanation, and hers best for true-false.
    Exam questions at this level are best considered in the context of the course and the teacher - which is why I asked about what your teacher would normally be referring to.
     
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