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A high powered laser beam (lambda= 630 nm) with a beam diameter of 0.1 m is aimed at the Moon, 3.8 xx 10^8 m distant. The beam spreads only because of diffraction, The angular location of the edge of the central diffraction disc is given by sin theta=(1.22 lambda)/(d) where d is the diameter of the beam aperture. What is the diameter of the central diffraction disc on the Moon's surface ? |
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Answer» 1010.2m Now angular speed `theta=("Diameter of central disc on moon")/("Distance of moon")` Diameter of central dic `=theta xx " Distance of moon"` `=(1.22 LAMBDA)/(d). D [therefore THET approx sin theta=(1.22lambda)/(d)]` Now `D=3.8 xx 10^(8) m` and d=0.1m Diameter of the central disc `=(1.22 xx 650 xx 10^(-9) xx 3.8 X 10^(8))/(0.1)` =3013.4 m |
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