SKEDSOFT

Interference: Light is an electromagnetic wave. The energy in such a wave is due to the electric and magnetic field vectors associated with them. In all electromagnetic waves, the electric and magnetic field vectors are mutually perpendicular to each other and also perpendicular to the direction in which the wave propagates(transverse wave).

When two light waves cross each other, due to superposition, the distribution of energy in space may takes place. This is similar to the superposition of any two waves like mechanical, sound etc. It is possible that in some region of space the energy is more than the energy due to individual waves and in some other region of space, it is less than that due to individual waves. The phenomenon of redistribution of energy due to superposition of waves is called interference. This redistribution of energy depends upon the frequency, amplitude and the phases of individual waves. In the following, we shall be discussing these phenomenon and the conditions to observe interference.

Superposition of Waves: Consider two light waves each of frequency , propagating along z axis in vacuum.

Let for the sake of simplicity, both the waves be linearly polarized (i.e. the electric field vector is along a line) with Electric field along the x-axis.

Let the phases of individual waves at a given point in space be and The waves can be written as

                                          -------------------------- (1)

                                          -------------------------- (2)

The resultant wave is given by

                                                                  ------------------------- (3)

       =

       =

                                            ---------------------------(4)

Fig.1:Resultant of two linearly polarized waves ( & ).