Question

An electromagnetic wave travels in vacuum along z direction: `E = ( E_1hati + E_2hatj ) cos (kz - ωt)`. Choose the correct options from the following:

1. The associated magnetic field is given as `B = 1/c(E_1hati - E_2hatj) cos (kz - ωt)`.
2. The associated magnetic field is given as `B = 1/c(E_1hati - E_2hatj) sin (kz - ωt)`.
3. The given electromagnetic field is circularly polarised.
4. The given electromagnetic wave is plane polarised.

Options

• a and b

• b and c

• c and d

• a and d

Answer 1

a and d

Explanation:

We are given that the electric field vector of an electromagnetic wave travels in a vacuum along z-direction as `vecE = (E_2hati + E_2hatj) cos (kz - ωt)`

The magnetic of the electric and the magnetic fields in an electromagnetic wave are related as `B_0 = E_0/c`

`vecB = vecE/c = (E_1hati + E_2hatj)/c cos (kz - ωt)`

Also, `vecE` and `vecB` are perpendicular to each other and the propagation of electromagnetic wave is perpendicular to `vecE` as well as `vecB`, so the given electromagnetic wave is plane polarized.