Problem 31.42 Part A At one instant, the electric and magnetic fields at one Wha

Question

Problem 31.42 Part A At one instant, the electric and magnetic fields at one What is the value of a? point of an electromagnetic wave are E = (250i + 3403-60kV/m and B = (7.5i-7.7j + | Express your answer using two significant figures ak)Bo. a= Submit My Answers Give Up Part B What is the value of Bo? Express your answer using two significant figures AT Submit My Answers Give Up Part C What is the Poynting vector at this time and position? Find the z-component. Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

A] we know that E.B = 0

250*7.5 -340*7.7 - 60a = 0

a = [ 250*7.5 -340*7.7]/60 = -12 answer

B] |B| = E/c = sqrt(250^2+340^2+60^2) /3e8 = 1.421e-6

B0 = 1.421e-6/sqrt(7.5^2+7.7^2+12.383^2) = 0.087*10^-6 T = 0.087 uT answer

c] poynting vector S = 1/u0 E x B

Sx = 1/[4pi *10^-7] *(340*12 - 60*7.7)*8.7e-8 = 2.5*10^2 W/m^2

d] Sy = 1/[4pi *10^-7] *(-60*7.5 - 250*12) *8.7e-8 = -2.4*10^2 W/m^2

e] Sz = 1/[4pi *10^-7] *(250*-7.7 - 340*7.5) *8.666e-8 = -310 W/m^2

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