Question 7: EM waves

Question

The electric and magnetic fields associated with an electromagnetic wave propagating along +z axis, can be represented by

Accepted Answer

For a wave travelling along +z, the fields must satisfy
$E\perp B$,
$E	imes B$ points in the +zÃ¢ÂÂdirection (thatÃ¢ÂÂs the Poynting vector).
Checking each option:
Option A: $E=E_0\,\hat i,\;B=B_0\,\hat j$ gives
$     E	imes B = E_0B_0\,(\hat i	imes\hat j)=E_0B_0\,\hat k   $
which is +z.
All other choices give the wrong propagation direction.
Answer: Option A.

Answer

$E=E_0 i, \quad B=B_0 j$

Answer

$E=E_0 i, \quad B=B_0 k$

Answer

$E=E_0 k, \quad B=B_0 j$

Answer

$E=E_0 j, \quad B=B_0 k$

EM waves

The electric and magnetic fields associated with an electromagnetic wave propagating along +z axis, can be represented by

Choose the correct answer: