JEE Main & Advanced Physics EM Waves JEE PYQ-Electro Magnetic Waves

For plane electromagnetic waves propagating in the z direction, which one of the following combination gives the correct possible direction for \[\overset{\to }{\mathop{E}}\,\]and \[\overset{\to }{\mathop{B}}\,\]field respectively? [JEE MAIN 11-04-2015]

A) \[\left( \hat{i}+2\hat{j} \right)\]and\[\left( 2\hat{i}-\hat{j} \right)\]

B) \[\left( -2\hat{i}-3\hat{j} \right)\]and\[\left( 3\hat{i}-2\hat{j} \right)\]

C) \[\left( 2\hat{i}+3\hat{j} \right)\]and\[\left( \hat{i}+2\hat{j} \right)\]

D) \[\left( 3\hat{i}+4\hat{j} \right)\]and\[\left( 4\hat{i}-3\hat{j} \right)\]

Correct Answer: B

Solution :

[b] In propagation of light \[\vec{E}\]and \[\vec{B}\]oscillate in mutually perpendicular directions.

\[\vec{E}\times \vec{B}=\]direction of propagation = +z direction only option [d] satisfies both conditions of [a] \[\vec{E}\times \vec{B}=0\]

[b] \[\left( \vec{E}\times \vec{B} \right)\]directed along the z-axis.