Interference is a sub topic in physics and a chapter in applied physics or engineering physic in BTech not only in btech but also in science related under graduation. Th PDF starts with simple definition of coherence, types of coherences, division of amplitude and conference in thin and think film. It also has brief description as well as derivation for formulas for each case. Newtons Rings experiment is also included with the pictorial presentation. Newtons rings experiment is also observed in physics laboratory for B.Tech students.