What I Know Let Us determine how much you already know about Interference and Diffraction. IDENTIFY. He is a Dutch physicist who states that if the position of a wave front at one instant is known, then the position of the front at a later time can be constructed by imagining the front as a source of secondary wavelets. It is a type of interference that occurs when the two interfering waves have a displacement in the same direction, therefore, they are \"in-phase\" and will combine together and increase the amplitude. This principle refers to the bending or spreading of a wave through an opening or an obstacle. This principle states that when two or more waves overlap, the resultant displacement at any point and at any instant is found by adding the instantaneous displacements that would be produced at the point by the individual Waves if each were prosent alone. This phenomenon occurs when two or more waves pass through the same region at the same time. a What I Have Learned .' In your own words, describe the following: Interference