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?

• A. Positive direction of $z$
• B. Negative direction of $y$
• C. Positive direction of $x$
• D. Negative direction of $x$

Answer 1

Answer: (C)

Positive direction of $x$

Answer 2

As, poynting vector
S=E×H
Given energy transport = negative z direction
Electric field = positive y direction
(−k^)=(+j^​)×[i^]
Hence according to vector cross product magnetic field should be positive x direction.