All electromagnetic wave is transporting energy in negative z direction. At a certain point and cert

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8.Electromagnetic waves

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All 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?

A

Positive direction of $x$

B

Positive direction of $z$

C

Negative direction of $x$

D

Negative direction of $y$

(JEE MAIN-2023)

Solution

As, poynting vector

$\overrightarrow{ S }=\overrightarrow{ E } \times \overrightarrow{ H }$

Given energy transport $=$ negative $z$ direction Electric field $=$ positive $y$ direction

$(-\hat{ k })=(+\hat{ j }) \times[\hat{ i }]$

Hence according to vector cross product magnetic field should be positive $x$ direction.

Standard 12

Physics

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