【2017年整理】17光的衍射.ppt

O 设光栅总缝数为N,平行光垂直入射,每缝光束振幅 P (1)缝间干涉—多光束干涉 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 相邻两缝光束的光程差均为 P点合振幅: Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. O 用多边形法则叠加 (最大) (最小) A=Na A=0 0ANa Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. (10) 主极大明纹条件——光栅方程 条纹位置: 讨论: 当 时, 光栅常数越小,条纹越分得开; 对k 有限制. ? 小的条纹密; ——光强最强 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. (20) 暗纹条件 当 时, 在相邻两个主极大明纹之间有(N-1)个暗纹, 还有(N-2)个光强很小的次极大明纹. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. (2)单缝衍射的影响 理论计算表明: 缝间干涉形成的主极大光强受单缝衍射光强分布的调制,使得各级主极大的光强大小不同。 如 N = 4 ,相邻两个主极大之间有 3 个极小和 2 个次极大: Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 单缝衍射因子 缝间干涉因子 用菲涅耳积分法可得光强分布为 式中: Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. * 第 十 七 章 光 的 衍 射 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 主要内容: 1.惠更斯---菲涅耳原理; 2.单缝衍射 、光栅衍射; 3.圆孔衍射、光学仪器的分辨率; 4. X射线的衍射。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. §17-1 光的衍射现象 一.光的衍射现象 光绕过障碍物偏离直线传播,进入几何阴影区,使光强重新分布的现象。 惠更斯---菲涅耳原理 缝 屏 光源 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 惠更斯原理: 波面上任一点均可视为能发射子波的波源,其后任一时刻,这些子波的包络面就是新的波面。 波面上任一点均可视为能发射子波的波源, 波面前方空间某点的光振动取决于到达该点的所有子波的相干叠加。 惠更斯-菲涅耳原理: 二.惠更斯-菲涅耳原理 Evaluation only. Created with Aspose.Slides