Maxwell's Theory

In Chapter 2, we discussed the wave theory of light, developed a model to superimpose waves, and described the resulting interference pattern in terms of intensity depending on wavelength. The model was based on the scalar wave equation, but in additionwemade reference to electromagnetic theory.We needed to take into account that a light wave changes its wavelength when traveling through a medium of refractive index n and also used Fresnel’s formulas. Electromagnetic theory is described by Maxwell’s equations. The first hint that light is electromagnetic radiation came from electromagnetic experiments not involving visible light. In the analysis of the experiment a constant appeared which had the value of the speed of light. From relativity theory we know that the speed c of light is a fundamental constant and the ultimate limit of speed. We derive from Maxwell’s theory and the laws of reflection and refraction, as we assumed in the chapter on geometrical optics, that light travels in straight lines. We also may derive from Maxell’s equations what we used in the chapters on interference and diffraction and obtained from the scalar wave equation.