The Blackbody Spectrum

Click this link of the Blackbody Spectrum simulator. If you are using a printed version of this
document, then type this link on your internet browser.
Ensure the “Graph Values” is checked. See the image on the right.
You can control the blackbody temperature, and notice that for every given
temperature the peak of the spectrum corresponds to a particular wavelength.
For example, if the temperature is T = 5350 K the peak corresponds to the
lambda Ȝpeak = 0.542 ȝm. See the snapshot below:
Fill in the following table of Ȝpeak values for every temperature T and calculate 1/T. For this part,
you may use any spreadsheet programs. We suggest using the Google Spreadsheet.
T (K) 1/T (K-1) Ȝpeak ȝm)

Created in Master PDF Editor

  1. Plot Ȝpeak vs 1/T using the scatter plot as you did in the previous experiment. Make a
    linear fit of the data (add a linear trendline) by selecting the intercept at zero. Display an
    equation of this fit on the chart. What value of “b” do you get? (Attach your plot to this
    lab report).
  2. Calculate the discrepancy error, |b – 2898| / 2898 × 100% and comment about your
    finding. Does it agree with the theoretical value?
  3. Using your value of b and the Wien’s Displacement equation, predict the surface
    temperature of a neutron star whose peak wavelength is observed in the x-ray region of
    Ȝpeak ȝm.
    T = _______________ K
  4. The normal human body temperature is T = 310 K. At what wavelength would humans
    emit the blackbody radiation? What region of the electromagnetic spectrum does it
    correspond to?
    Ȝpeak,human = _______________ ȝm.
  5. Can you now explain why blue stars hotter than the red stars?

Sample Solution