Principle objective of this lecture is to present on Two Source Interference. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium. Wave interference can be constructive or destructive in nature. Constructive interference occurs at any location along the medium where the two interfering waves have a displacement in the same direction. Destructive interference occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction.