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Color Temperature of a Blackbody Source

Excel
                  version
Excel version   [Mathematical Basis]

Evaluation of the Planck blackbody equation. Demonstrates how the emission spectrum of a blackbody radiator depends on its temperature and emissivity.

This model can be used to determine whether a light source has a blackbody-like emission spectrum and to estimate its temperature and emissivity if so. Students take experimental measurements of the radiance of a light source at various wavelengths, type in the values of wavelength and radiance into the table on the right, then adjust the parameters of the model (temperature and emissivity) so that the calculated blackbody spectrum (shown by the red line) is a best fit to the experimental data points (shown by the blue dots).

Download links:
Download spreadsheet in Excel format (.xls)
Download spreadsheet in OpenOffice format (.ods)

WingZ version: black.wkzScreen image.
Wingz player application and basic set of simulation modules, for windows PCs or Macintosh

Other simulations that employ a blackbody source:
Signal-to-Noise Ratio of Absorption Spectrophotometry
Fluorescence Spectroscopy Signal-to-Noise Ratio
U.V.-Visible Spectrophotometer
Dual Wavelength Spectrophotometer

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Mathematical basis

Blackbody temperature, T (in degrees K), set by on-screen slider.
Emissivity, set by on-screen slider.
Calculated radiance = emissivity*1.19111E+16*wavelength^(-5)/(exp(14380000/(wavelength*T))-1)
The graph shows a plot of calculated radiance (red line) and measured radiance (blue dots)
vs wavelength

OpenOffice Calc and Excel Versions



Computes the spectral radiance, total radiance, and peak wavelength of a blackbody source, given the temperature and emissivity. Also plots spectral radiance vs wavelength from 150 nm to 3500 nm.

View Equations (.pdf)

Note: to run the OpenOffice (.ods) spreadsheets, you have to first download the OpenOffice installer (download from OpenOffice), then install it (by double-clicking on the installer file that you just downloaded), and then download my spreadsheets from this page.  Once OpenOffice is installed, you can run my spreadsheets just by double-clicking on them.


(c) 1991, 2013, Prof. Tom O'Haver , Professor Emeritus, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu.
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