If a 20 W laser beam,which has an initial diameter of 2.0 mm,spreads out to a diameter of 2.0 m after traveling 10,000 m,what is the final intensity of the beam? A) 20 $\times$ 10^-4 W/m² B) 20 $\times$ 10^-6 W/m² C) 20 $\times$ 10^-8 W/m² D) 6.4 W/m² E) 6.4 $\times$ 10^-6 W/m²

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The Answer of If a 20 W laser beam,which has an initial diameter of 2.0 mm,spreads out to a diameter of 2.0 m after traveling 10,000 m,what is the final intensity of the beam? A) 20 $\times$ 10^-4 W/m² B) 20 $\times$ 10^-6 W/m² C) 20 $\times$ 10^-8 W/m² D) 6.4 W/m² E) 6.4 $\times$ 10^-6 W/m²

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