p37_026

# p37_026 - up by the telescope is then = ( d /d 3 ) 2 ....

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26. We denote the Earth-Moon separation as L . The energy of the beam of light which is projected onto the moon is concentrated in a circular spot of diameter d 1 ,where d 1 /L =2 θ R =2(1 . 22 λ/d 0 ), with d 0 the diameter of the mirror on Earth. The fraction of energy picked up by the reﬂector of diameter d 2 on the Moon is then η 0 =( d 2 /d 1 ) 2 . This reﬂected light, upon reaching the Earth, has a circular cross section of diameter d 3 satisfying d 3 /L =2 θ R =2(1 . 22 λ/d 2 ). The fraction of the reﬂected energy that is picked
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Unformatted text preview: up by the telescope is then = ( d /d 3 ) 2 . Consequently, the fraction of the original energy picked up by the detector is = = d d 3 2 d 2 d 1 2 = d d 2 (2 . 44 d em /d )(2 . 44 d em /d 2 ) 2 = d d 2 2 . 44 d em 4 = (2 . 6 m)(0 . 10 m) 2 . 44(0 . 69 10 6 m)(3 . 82 10 8 m) 4 4 10 13 ....
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