Interference

In Chapter 1 we described image formation by light, using our model which states that light propagates along straight lines and utilizes the laws of reflection and refraction.We now consider the wave nature of light. In the famous experiment by ThomasYoung, one observes on a screen an interference pattern, consisting of bright and not so bright stripes of light. The interpretation of an interference pattern was done by using an analogy to water waves. However, the water wave pattern is observed as an amplitude interference pattern whereas the superposition of light waves, also generated as an amplitude pattern, is observed as an intensity pattern. Historically, Newton associated the light beams of geometrical optics with a stream of particles and some scientists attacked Young in his time, saying that he was diminishing Newton’s work. Today we know that light is an electromagnetic wave but, in a complementary way, light is also described by quantum mechanics as an assembly of particles.