Shadows And Eclipses

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INTRODUCTION This project presents the principles, types, and application of shadows. The lore of shadows and its application to eclipses are also presented in detail. The lore of shadows, and its application to eclipses ________________________________________ Shadows happen when the illumination comes from a limited source, and convinces us that light travels in straight lines, or rays. Of course, we know that light is actually a wave, but that is another story that must be told elsewhere. We must look at shadows very closely indeed to discover any of the effects of the wave nature of light, and for now we can neglect it as an inconsiderable effect. Illumination that produces shadows has the first traces of coherence, in that all the rays proceed from approximately one point, or are stigmatic. This is a small regularity indeed, but it is enough to give us shadows. If, in addition, the light was of a narrow band of wavelengths, the further coherence would show us interesting frills and bands at the boundaries of the shadows. With laser illumination, these details are easily seen. There are positive shadows, when an opaque obstacle is located in the stigmatic illumination. We see them every sunny day, in the nearly parallel rays of the sun, which casts the most familiar sharp shadows. There are also negative shadows, when the obstacle is replaced by an aperture in an opaque screen. In either case, the form of the shadow can be found by tracing rays from the source through points on the boundary of the obstacle or aperture. When these rays fall on a surface, they mark the separation of light and shade. In the wide sense, a shadow is essentially a three-dimensional object, not a two-dimensional figure. Shadows allow us to determine the altitude or declination of the sun, and the heights of objects too high to scale easily. We simply apply the principles
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