EME 810
Solar Resource Assessment and Economics

3.4. Learning Activity: Laws of Light

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Wolfram Alpha website is the Google of math and physics. If you want to do calculations on Wien's Law, you type "wien's law" and you will get a calculator for Wien's Law with all sorts of other information. The purpose of this activity is to practice some basic calculations of physical properties of sunlight.

Short Problems:

  1. Use Wolfram Alpha to calculate the most probable wavelengths emitted by the surface of the Earth (T=300 K) and the Sun (T=5778 K) using one or more of the laws discussed on the previous page of this lesson. What is the meaning of the "most probable wavelength"? 
  2. Use Wolfram Alpha to calculate the energy flux (radiant exitance) emitted by those Earth's and Sun's surfaces using Stefan-Boltzmann Law. 
  3. Apply the Inverse Square Law (see formula on page 3.2 of this lesson) to determine the "extraterrestrial solar flux" at the Earth using the Sun's radiant exitance found in Question 2. 
  4. Discuss the meaning of "extraterrestrial solar flux" and how it is further transformed within the Earth's atmosphere.

This video below (6 min) presents a short demo on how to use the Wolfram Alpha site. The Stefan-Boltzmann Law is used as an example here, so it provides you with a tip for solving the second problem. 

Wolfram Alpha Demo
Credit: M. Fedkin © Penn State University is licensed under CC BY-NC-SA 4.0

Submitting Your Work

Prepare a written report with your solutions and upload it to Canvas (Lesson 3 Learning Activity Dropbox) in PDF or docx format. You can use Wolfram Alpha screen shots to present your results for the first two problems (insert the screenshots into your report - don't submit them as separate files). Make sure to present the equations you are using and provide comments to the steps in your solutions.

Grading Criteria

View the Rubric in Canvas by which this assignment will be graded.

Deadline

See the Calendar tab in Canvas for specific due dates.