56. A small helium-neon laser emits red visible light with a power of 3.0 m W in a beam with a radius of 2.0 mm. Which of the following values is closest to the electric field amplitude of this light in V/m? (ε0=8.85 x10-12 C/N·m2)
(A)0.8
(B)5.0
(C)30
(D)400
(E)1000
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統計: A(0), B(1), C(1), D(2), E(0) #3091974
統計: A(0), B(1), C(1), D(2), E(0) #3091974