As we have assumed that the field components are independent of y and z eqn (5.34) reduces to

                              (5.35)

i.e. there is no variation of E_x in the x direction.

Further, from 5.33(a), we find that implies which requires any three of the conditions to be satisfied: (i) E_x=0, (ii)E_x = constant, (iii)E_x increasing uniformly with time.

A field component satisfying either of the last two conditions (i.e (ii) and (iii))is not a part of a plane wave motion and hence E_x is taken to be equal to zero. Therefore, a uniform plane wave propagating in x direction does not have a field component (E or H) acting along x.

Without loss of generality let us now consider a plane wave having E_y component only (Identical results can be obtained for E_z component) .