Question 79: EM waves

Question

An electromagnetic wave is transporting energy in the negative $z$ direction. At a certain point and certain time the direction of electric field of the wave is along positive $y$ direction. What will be the direction of the magnetic field of the wave at that point and instant?

Accepted Answer

As, poynting vector
$
\overrightarrow{\mathrm{S}}=\overrightarrow{\mathrm{E}} 	imes \overrightarrow{\mathrm{H}}
$
Given energy transport $=$ negative $\mathrm{z}$ direction
Electric field $=$ positive $\mathrm{y}$ direction
$(-\hat{\mathrm{k}})=(+\hat{\mathrm{j}}) 	imes[\hat{\mathrm{i}}]$
Hence according to vector cross product magnetic field should be positive $\mathrm{x}$ direction.

Answer

Negative direction of $y$

Answer

Positive direction of $z$

Answer

Positive direction of $x$

Answer

Negative direction $x$

EM waves

An electromagnetic wave is transporting energy in the negative z direction. At a certain point and certain time the direction of electric field of the wave is along positive y direction. What will be the direction of the magnetic field of the wave at that point and instant?

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