42.What is the average value of the magnitude of the Poynting vector at 1 meter from a 100-watt lightbulb radiating uniformly in all directions?
(A) 1 W/m2
(B) 2 W/m2
(C) 4 W/m2
(D) 8 W/m2
(E) 16 W/m2
答案:登入後查看
統計: A(1), B(1), C(1), D(6), E(1) #3427042
統計: A(1), B(1), C(1), D(6), E(1) #3427042