Question

An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point towards.

• A. North
• B. East
• C. West
• D. Downwards

Answer 1

Answer: (B)

East

As the electromagnetic wave is the crossed field of electric and magnetic waves, so the direction of propagation of EM wave is the direction of vector $E\times B$. Here E is upward and $(E\times B)$ is towards the north.
So, from right-hand thumb rule B will be along the east.