6 Diffraction

6.1 Diffraction—A Historical Perspective

In the last chapter, we saw that light travelling through a small pin hole opening or narrow slit resulted in an image that was spread out. The reason the image was not perfectly sharp has to do with the wave nature of light. Light does not travel in a straight line as would be expected from geometrical optics. This spreading out of light after passing through the pin hole or narrow slit finds its explanation only after considering the wave nature of light. Upon close examination, we see alternate bright and dark areas. A simple experiment can be done to demonstrate this spreading out of light. Take two closely spaced straight edges and then view a distant light source between them. What ...

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