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Planck Radiation Laws: Excel; Mac or PC

Activity and Starting Point page by R.M. MacKay. Clark College, Physics and Meteorology.
This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.

Summary

Students use an existing Excel workbook to investigate how spectral irradiance from a blackbody radiator depends on temperature, and to clearly see the connection between Planck's Radiation law, and the Stefan-Boltzman and Wien Radiation laws. Students adjust the solar temperature to get the best fit between observations and the spectral irradiance calculated from Planck's Radiation Law for a blackbody radiator. Two sets of observational based solar spectral irradiance are included for comparison.

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Learning Goals

  • Planck Radiation Law
  • Wien's Law
  • Stefan-Boltzman Law
  • Blackbody Spectrum
  • Observed solar vs. spectral irradiance from Planck Radiation Law
  • Estimate solar temperature

Context for Use

Useful in introductory courses in Meteorology, Atmospheric Science, Climate Change, or Earth Systems Science when studying radiative transfer in the atmosphere.

Description and Teaching Materials

The Excel Workbook XLPlanck (Excel 622kB Apr3 04) contains 6 sheets:

  • A suggested student activity/questions sheet
  • Two independent sets of solar spectral irradiance data
  • Planck Radiation Law with scale for clear graphs of T=100K to 1000K
  • Planck Radiation Law with scale for clear graphs of T=1000K to 10000K
    • Students can use the above two sheets to see how spectral irradiance depends on temperature, and to clearly see the connection between Planck's Radiation law, and the Stefan-Boltzman and Wein Radiation laws.
  • Graphs of Planck Model and top of atmosphere spectral irradiance (old). Students can change the solar temperature to get the best fit of model to observations.
  • Graphs of Planck Model and top of atmosphere spectral irradiance (new) (more info) . Students can change the solar temperature to get the best fit of model to observations.

Teaching Notes and Tips

The Excel document can be used for the following purposes:
  • Student interactive activity for lab or homework
  • Introducing concepts and ideas in an interactive lecture
  • Making transparencies or power point slides
  • Checking student results

The Excel activity take about 2 hrs to work through. Students more familiar with Excel can do it more quickly. It is assumed that students have some previous experience with the Excel environment.

Using the JAVA applets in the resources section below in either an interactive lecture or interactive student-centered learning experience may prove useful.


Assessment

Completion of the activity is one measure of student success.

sunII sheet of the XLPlanck workbook

The figure is from the sunII sheet of the XLPlanck workbook after the Planck model temperature has been adjusted to fit the observed spectral irradiance values. (click image to enlarge)

References and Resources

The Planck Radiation Law (more info) site introduces Planck's model equation for the spectral irradiance of a black-body radiator and the connection between the Planck Radiation Law, and the Stefan-Boltzman and Wein radiation laws. This site has connections to three on-line interactive JAVA Applets:

  • Planck Radiation Law;
  • Wien's Law, Stefan-Boltzmann Law, and Color Indices;
  • BlackBody: The Game!;

The JAVA Applet BlackBody is great for interactive lectures or student use as it surperimposes the visible spectrum on the Planck radiation curve. Care must be taken when using JAVA Applets in that they may not work on all browsers.

Resources on getting started with Excel are available HERE.