# Introduction

A changing electric field produces a changing magnetic field and vice versa which gives rise to a transverse wave known as electromagnetic wave. The time-varying electric and magnetic field are mutually perpendicular to each other and also perpendicular to the direction of propagation of this wave (Fig. 1).

The electric vector is responsible for the optical effects of an EM wave and is called the

*light vector*.**Fig. 1**

- and always oscillate in phase.
- and are such that is always in the direction of propagation of wave.

**Fig. 2**

- The EM wave propagating in the positive
*x*-direction may be represented by*E*=*E*=_{y}*E*_{0}sin (*kx*â€“*Ï‰t*)*B*=*B*=_{z}*B*_{0}sin (*kx*â€“*Ï‰t*)*E*(or*E*),_{y}*B*(or*B*) are the instantaneous values of the fields,_{z}*E*_{0},*B*_{0}are amplitude of the fields and*K*= angular wave number 2*Ï€**Î»*.