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A telescope can be used to enlarge the diameter of a laser beam and limit diffraction spreading. The laser beam is sent through the telescope in opposite the normal direction and can then be projected onto a satellite or the Moon. (a) If this is done with the Mount Wilson telescope, producing a 2.54-m-diameter beam of 633-nm light, what is the minimum angular spread of the beam? (b) Neglecting atmospheric effects, what is the size of the spot this beam would make on the Moon, assuming a lunar distance of $3.84 \times 10^8 \textrm{ m}$?
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Final Answer
  1. $3.04 \times 10^{-7} \textrm{ rad}$
  2. $236 \textrm{ m}$
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OpenStax College Physics Solution, Chapter 27, Problem 61 (Problems & Exercises) (3:08)

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