Intensity distribution:

We have seen in the earlier sections, that whenever two waves superimpose the resultant wave's amplitude gets modified. If the two superimposing waves are of same frequency and wave vector, then the amplitude (thus intensity) at any time and position depends upon the phase difference between the two propagating waves. As these waves are traveling waves, at a given time t, the phase of the waves vary with the position in space. Now if we consider the superposition of these waves at different points in space (at time t), the intensity will depend upon the relative phase difference between the two waves, at these points, where the phase difference between the waves in even multiple of , the intensity will be maximum and more than the sum of intensity of individual waves ; where as at points where the phase difference is odd multiple of , the intensity will be minimum and is less than the sum of intensity of indivisual waves .

At all other points, intensity will be between this maximum and minimum intensity depending upon the phase difference. Fig ………….shows the variation of intensity with phase difference between the two waves. This spatial variation of intensity gives the interference pattern on screen.