TABLE OF CONTENTS The phenomenon of the interference of light has proved the validity of the wave theory of light. According to it, when two light waves of the same frequency and having a constant phase difference traverse simultaneously in the same region of a medium and cross each other, then there is a modification in the intensity of light in the region of the superposition, which is in general different from the sum of intensities due to individual waves at that point. This modification in the intensity of light resulting from the superposition of two (or more) waves of light is called interference. At certain points the waves superimpose in such a way that the resultant intensity is greater than the sum of the intensities due to individual waves. The interference produced at these points is called constructive interference or reinforcement, while at certain other points the resultant intensity is less than the sum of the intensities due to individual waves. The interference produced at these points is called destructive interference. Beyond the region of superposition the waves come through completely uninfluenced by each other.
