Sorry if I am posting in the wrong place. I'm really interested in the Fourier series, but I'm not an expert on it yet. I am very well aware yoy can do it with sound waves, but can you manipulate any other waves? What about light waves? And for absorption, how can you measure the absorption of light/sound waves of a material? Or better yet, how can you measure the amount of penetration through a material of light/sound waves?