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A laser has lambda= 7xx 10^(-7)m and aperature 10^(-3)m sends a beam to Moon which is at a distance of 4xx 10^(8)m from the Earth. Deduce the angular spread of the beam and the areal spread as it reaches Moon. |
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Answer» Solution :We are given that `lambda= 7xx 10^(-7)m, a= 10^(-3)m, D= 4xx 10^(8)m` CLEARLY, angular SPREAD, `theta= (lambda/a)= (7xx 10^(-7)m)/(10^(-3)m)= 7xx 10^(-4)rad` Linear spread, `X= D theta` `=(4XX10^(-8)m)(7xx 10^(-4))= 28xx 10^(4)m` Areal spread `x^(2)= (28xx 10^(4)m)^(2)= 7.84xx 10^(10) m^(2)`. |
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