At one instant, the electric and magnetic fields at one point of an electromagne

Question

At one instant, the electric and magnetic fields at one point of an electromagnetic wave are E-(220i + 300 j-60kV/m and B-(7.8?-73jt ak)Bo. ? Part A What is the value of a? Express your answer using two significant figures Correct ? Part B What is the value of Bo? Express your answer using two significant figures ??? Bo= 7.11 AT Submit Previous Answers Request Answer X Incorrect, Try Again; 5 attempts remaining 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 s-3400 |

Explanation / Answer

(A) E and B are perpendicular so E.B = 0

(220 x 7.8) + (300 x -7.3) + (-60 x a) = 0

a = - 7.9  

(B) |E| = sqrt(220^2 + 300^2 + 60^2) = 376.83 N/C

|B| = sqrt(7.8^2 + 7.3^2 + 7.9^2) Bo = 13.29 B0

and |E| = c |B|

376.83 = (13.29 x Bo) (3 x 10^8)

Bo = 9.5 x 10^-8 T Or 0.095 uT  

Ans: 0.095

(C) S = (E x B) / u0

  
Sx = ((300 a) - (-60 x -7.3))B0 / u0

Sx = - 212.3 W/m^2

Ans: - 210 W/m^2

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