Although it originates from the ancient Greeks, optics still arouses a lot of scientific interest, mainly due to the technological innovation associated with it. One of its most interesting applications is related to optical metrology and the characterization of materials through optical techniques. While some of these processes can be explained in a simplified way using a few of the fundamental principles of physics, there are hardly any proposals whose objective is to discuss this topic at a basic level. Accordingly, we present a low-cost experiment that allows the characterization of surface roughness using the fractal dimension of the speckle pattern associated with the light scattered by a surface. For simplicity, the entire activity is adaptable to the most diverse school situations. Moreover, it allows the discussion of many fundamental physics concepts and provides students with an experience similar to that experienced by scientists.

尽管它起源于古希腊人，但光学技术仍然引起了很多科学兴趣，这主要是由于与之相关的技术创新。它最有趣的应用之一与光学计量和通过光学技术表征材料有关。尽管可以使用一些物理学的基本原理以简化的方式来解释其中的一些过程，但是几乎没有任何提案的目的是在基本层面上讨论该主题。因此，我们提出了一个低成本的实验，该实验允许使用与由表面散射的光相关的斑点图案的分形维数来表征表面粗糙度。为简单起见，整个活动适用于最多样化的学校环境。而且，