根据朗伯定律，单色光照射均匀介质时，介质对光强的衰减程度与介质厚度成正比，就像穿过越来越厚的雾气，能见度逐渐降低： dIt/It=﹣μdt 其中，μ是衰减系数，表示该物质对入射X射线的线衰减系数。物理上，它代表单位长度物质引起的相对衰减量。积分后得到这个优雅的指数衰减公式：It​=I0​e−μt 这里t是介质厚度，It​/I0称为穿透系数，It​为透射强度，I0​为入射强度。 这个公式告诉我们，X射线强度随着穿透深度的增加而指数衰减。---**Textual Information:** (2) X射线的衰减 **Chart/Diagram Description:** * **Type:** Schematic diagram illustrating the attenuation of radiation passing through a material. * **Main Elements:** * A rectangular block representing a material is shown in light green with wavy sides. * Red arrows point downwards, entering the top surface and exiting the bottom surface, representing the direction of radiation. * The initial intensity of the incoming radiation is labeled as $I_0$ near the top surface, above the incoming arrows. * The intensity of the outgoing radiation after passing through the material is labeled as $I$ near the bottom surface, below the outgoing arrows. * The total thickness of the material block is labeled as $t$ on the right side, indicated by a vertical double-headed arrow connecting the top and bottom surfaces. * A small, dark green rectangular region is shown inside the material block. * The thickness of this small region is labeled as $dt$ on the left side, indicated by a vertical double-headed arrow connecting the top and bottom of the small region. * Horizontal lines mark the top and bottom surfaces of the material and the top and bottom boundaries of the differential thickness layer $dt$.