3 Light and telescopes

http://www.teachastronomy.com/astropedia/article.aspx?qid=258
http://www.teachastronomy.com/astropedia/article.aspx?qid=259
http://www.teachastronomy.com/astropedia/article.aspx?qid=260
http://www.teachastronomy.com/astropedia/article.aspx?qid=261
http://www.teachastronomy.com/astropedia/article.aspx?qid=262
http://www.teachastronomy.com/astropedia/article.aspx?qid=263
http://www.teachastronomy.com/astropedia/article.aspx?qid=264
http://www.teachastronomy.com/astropedia/article.aspx?qid=265

http://www.teachastronomy.com/astropedia/article.aspx?qid=266

http://www.teachastronomy.com/astropedia/article.aspx?qid=267
http://www.teachastronomy.com/astropedia/article.aspx?qid=269
http://www.teachastronomy.com/astropedia/article.aspx?qid=270
http://www.teachastronomy.com/astropedia/article.aspx?qid=271
http://www.teachastronomy.com/astropedia/article.aspx?qid=272
http://www.teachastronomy.com/astropedia/article.aspx?qid=273

http://www.teachastronomy.com/astropedia/article.aspx?qid=274
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http://www.teachastronomy.com/astropedia/article.aspx?qid=280
http://www.teachastronomy.com/astropedia/article.aspx?qid=281
http://www.teachastronomy.com/astropedia/article.aspx?qid=282
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http://www.teachastronomy.com/astropedia/article.aspx?qid=284
http://www.teachastronomy.com/astropedia/article.aspx?qid=285

http://www.teachastronomy.com/astropedia/article.aspx?qid=276
http://www.teachastronomy.com/astropedia/article.aspx?qid=277
http://www.teachastronomy.com/astropedia/article.aspx?qid=278
http://www.teachastronomy.com/astropedia/article.aspx?qid=279

http://astro.unl.edu/classaction/light.html
http://astro.unl.edu/classaction/telescopes.html