Electromagnetic energy travels in waves. Energy, wavelength, and frequency of electromagnetic radiation are mathematically related. The range of wavelengths that electromagnetic radiation can exhibit is described by the electromagnetic spectrum.

The case-in-point for this section discussed how sunscreens work. Let's go into a little more depth. Richard Cornelius and colleagues from Lebanon Valley College in Pennsylvania took the spectra of a couple of the key ingredients in sunscreens, one of which we discuss in the text, and one that is quite similar to another we presented. Please see the paper at http://icarus.cc.uic.edu/~harwood/spectrosc_sun.pdf. You'll need to find a computer with an Adobe Acrobat reader to do so. Please answer the following two questions: 1. What do the experimenters use to dissolve the ingredients for their analysis, and why? 2. Note the spectra for these sunscreens. Given their absorbance maxima (related to the "molar absorptivity" listed), why do they work as sunscreens?

Photosynthesis is a model process for using the Sun's energy to power chemical processes.

Let's "virtually" travel to The University of Sydney in Australia for our next assignment. The have a photosynthesis simulator at http://fybio.bio.usyd.edu.au/VLE/L1/ResourceCentre/CAL/PSexpt/PSexpt.htm. Please be patient because it takes a few moments to load. Please read the instructions on the screen (three pages of information will appear). Then run the wavelength-based simulation. Print out (or write) the data for mL O2 produced versus wavelength of light (remember to click on the lamp to start each simulation). How does the oxygen produced at the different wavelengths coincide with the chlorophyll a absorbance spectrum in your text?

Atoms can absorb or emit light energy that is characteristic of that element. We can use the resulting emission or absorption spectrum in chemical analysis.

Varian Scientific Instruments is one of the most well known companies in the field of chemical analysis. Their web page, at http://www.varianinc.com/cgi-bin/nav?varinc/docs/osi/aa/atworks/AA_Index&cid=206618#aa76, has links to many types of analyses of ecological, industrial and biological importance. Pick an analysis from the list. Please describe it, and discuss how emission or absorption spectroscopy is critical to the analysis.

Electron exchange occurs in many chemical reactions. The electron exchange that occurs in spontaneous reactions can be used to power devices ranging from small appliances to motor vehicles.

Are there governments pushing for fuel cell technologies to be used in their countries? If so, which ones? How do you know? Please write an essay using reliable Web references to discuss the positions of governments in at least three countries regarding fuel cells. Please use references that are less than two years old. Cite spending levels as a way to support your discussion.

Photovoltaics is concerned with the generation of an electric current from solar power interacting with a material. Photovoltaic materials are semiconductors, most often made by combining "electron-rich" and "electron-deficient" materials with silicon.

What is the "million solar roofs" program, and why is it important? Is the program successful? Why or why not? For further information, please start at this site, http://www.eren.doe.gov/millionroofs/

This is as much a political and economic question as it is a scientific question.

Is the large-scale use of solar energy likely to be economically and politically viable? Argue the point using data from several Web sites. Here is a good starting point, http://www.solarbuzz.com/, the Solarbuzz Information Center.