The Interaction Between Light and Matter
What happens when light meets matter? There is always an interaction: light is scattered at a wall’s surface, reflected off a surface of water, partially absorbed and partially reflected by a green leaf, refracted when it enters glass, and excites chemical processes in retinal rods and cones, even at very low intensities. The details depend on the structure of the matter and on the wavelength of the light. Additional phenomena are refraction, diffraction, and fluorescence – even the miracle of transparency is fascinating. How is it possible that light passes almost completely unimpeded through a structure like the cornea or through water molecules? In this chapter, we discuss how light is affected by matter. In Chap. 7, we will discuss the special action of light on tissues.