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Error in percent transmission

  1. Dec 3, 2015 #1
    1. The problem statement, all variables and given/known data
    Hello,

    I've been using a light spectrometer to try to measure the reflectance of a sample of a protein I have on a glass slide. I followed the manual's instructions and first took a dark spectrum and a reference spectrum. However, the intensity was too high (far above the maximum recorded value of 4095 counts), so I used an aperture to reduce the amount of light released by the lamp I was using. This worked well, as for the reference spectrum I needed a peak at 3500 counts. However, when I looked at thee percent transmission, I noticed it was incredibly high (around 1000%). I placed a sample in there, just to test if that would improve anything, but it did not. Does anyone have experience with this and measuring the reflectance of samples?


    3. The attempt at a solution
    I thought that the angle of the slide might be relevant. Does anyone know how important the angle is in light spectrometry? Unfortunately, the sample is placed in a holder and, while the slide can touch anything, the sample itself cannot be contaminated, so I was forced to place it at a roughly 45 degree angle.
     
  2. jcsd
  3. Dec 6, 2015 #2

    mfb

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    Staff: Mentor

    1000% transmission doesn't make sense, you cannot transmit more than all light (100%). How did you get that value?
     
  4. Dec 6, 2015 #3
    That was the main problem. I was using a USB2000+ spectrometer to measure the transmission of light that was coming through a fiber optic cable. I'm not sure why the transmission is so high.
     
  5. Dec 6, 2015 #4

    mfb

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    Staff: Mentor

    Where does the number come from? DId you calculate it? Did some software calculate it based on input values (based on what)?
    It is hard to spot the problem if you don't explain what exactly you did.
     
  6. Dec 6, 2015 #5
    The number was calculated by the software based on the input from the USB2000+.
     
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