Mark,
Thanks for that -- I can't wait to either try it myself or suggest it to a class. Similar, but rather more immediate, is the CD spectrometer:
http://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html
For me, these tactile experiments are a compliment to the lessons I give on lighting simulation (so, not entirely OT then).
-John
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Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)