Question

For the electromagnetic wave represented by the equations E_y(x, t) = E_max cos(kx + Wt), B_z(x, t) = -B_max cos(kx + omega t), find the direction of the Poynting vector. in the - y -direction in the +x -direction in the +y -direction in the -x -direction Part B Find the average magnitude of the Poynting vector. Express your answer in terms of the variables E_max, B_max, and appropriate constants (mu 0 or epsilon_0). submit

Answer 1

A)

electric field is along the Y-direction and magnetic field in negative z-direction, hence the cross-product of electric field and magnetic field gives the direction as negative X-direction. hence poynting vector is in negative X-direction.

B)

poynting vector is given as

$\underset{S}{\rightarrow}$ = ($\underset{E}{\rightarrow}$ x $\underset{B}{\rightarrow}$ )/$\mu$

$\underset{S}{\rightarrow}$ = ((E_max Cos(kx + wt)) x B_max Cos(kx + wt))/$\mu$

$\underset{S}{\rightarrow}$ = (E_max B_max ) Cos²(kx + wt)/$\mu$