PHY136H5 Lecture Notes - Collimator, Diode, Doubleclick
Document Summary
When light or any other type of wave passes through an opening or goes by the edge of an obstacle, the wave extends (bends) into the region not directly exposed to the wave front. An explanation of this effect was first proposed by huygens (1629 . 1695), a contemporary of newton, in the light of a wave theory of light. Huygens" principle states that every point on a wave front can be considered as a source of tiny wavelets that spread out in the forward direction at the speed of the wave itself. The new wave front is the envelope of all the wavelets. So, when a wave front arrives at an opening, each point along the part of the wave front that extends across the opening sends out wavelets, all in phase, which spread out in all directions. The wave theory of light was not always widely accepted. The experiment was performed and the spot was found!
