Question

Choose the correct answer from the alternatives given.
An electromagnetic wave propagating along north lies its electric field vertically upward. The magnetic field vector points towards

• A. Downward
• B. East
• C. North
• D. South

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 north.
So, from right hand thumb rule B will be along east.