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Unformatted text preview: on the moon: W âˆ¼ L Î» D âˆ¼ (240000 miles) Â· 632 . 8 nm 1 cm âˆ¼ 15 miles. 1 Ph12a Solutions Problem Set 9 December 1, 2009 Figure 1: Geometry of problem 9.4 9.30 The circular wave a distance L from the source will appear to be planar in a circular region of radius R if its phase is approximately constant across this region. The maximum phase diï¬€erence will be between an edge and center of the region as shown in Fig. 2. The path diï¬€erence is given by p L 2 + R 2L â‰ˆ L (1 + R 2 2 L 2 )L = R 2 2 L . Hence the phase diï¬€erence Î” Ï† is Î” Ï† = 2 Ï€ Î» Ã— path diï¬€erence = Ï€R 2 LÎ» . Hence the phase is approximately constant over the plane of the circle to the extent that its area is small compared to LÎ» . 2 Ph12a Solutions Problem Set 9 December 1, 2009 Figure 2: Geometry of problem 9.30 . 3...
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 Spring '09
 DUDKO
 mechanics, Light, coherent, Visible spectrum

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