※ 引述《free94531 (FreeBlizzard)》之铭言： : 题目 : http://ppt.cc/SEbF : 告诉我算法就好了 不用真的算出来 : (a)我知道这一题是用波数(wave number)k 和w(omega)算 : 就是比较波动的公式 对吧?!@@ : (b)这题我没什麽头绪@@ : (c)好像是用u_av 公式算?! : 请各位大大解答~!!!感激~!!!!!! Problem3(15 points) Suppose the magnetic field(B) in a plane electromagnetic wave is given by B=jBy, where j is the unit vector along the y-direction, By=2*10^(-7)sin(0.5*10^3*x+1.5*10^11*t) Tesla, and the SI unit is adopted. (a)What are the wavelength and the frequency of this electromagnetic wave? wavelength: λ*0.5*10^3=2π λ=4π*10^(-3) frequency: T*1.5*10^11=2π f=1/T=(1.5*10^11)/2π (b)Write an expression for the electric field vector, including its direction. B=(1/ω) k×E E=iEx, where i is the unit vector along the x-direction, Ex=60sin(0.5*10^3*x+1.5*10^11*t) (c)What is the average intensity of this electromagnetic wave? I=(1/2)*c*ε*60^2 --

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