Applied Electro-Optics

3 Light and the Electromagnetic Spectrum

3.1 The Nature of Light

As we all know, our most important source of visible light is the sun. Those of us who have stayed out in the sunlight on a bright summer’s day a little bit too long also know that solar radiation contains damaging ultraviolet radiation. This energy somehow travels across the vacuum of space all the way to earth. But how does it get here? For a long time, many scientists thought that this energy was transmitted through a medium called the ether in a similar way that sound energy transmits through air. It was also proposed that this ether accounted for the finite velocity of light. This idea of an ether was needed to help explain how light energy could travel through the vacuum ...