The architecture of light: architectural lighting design concepts and techniques. A textbook of procedures and practices for the architect, interior designer and lighting designer pdfdrive com

Chapter 5 Physical Basics of Light

When we dedicate ourselves to incorporating light into our spaces, and claim it as a familiar medium, we also dedicate ourselves to understanding how light works. For our purposes, we will sail through a relatively succinct definition of what light is, how it interacts with the surfaces of our environment and how this affects our use of it. An understanding of light from a physical perspective will empower us to make good design decisions and avoid the perils and pitfalls of misapplied light.
Light is a member of a much larger family of physical phenomenon called
Electromagnetic Radiation. In our discussion, we will simply call it “radiation.” Radiation is responsible for many phenomena we encounter in our daily lives. It is all around us all of the time. X-Rays, Microwaves, Radio Transmission waves and even heat are all forms of radiation. “Light” is merely a name we have decided to give to the types of radiation that we are able to detect with our eyes.
LIGHT AS RADIATION
Radiation is essentially power and, as such, has no mass, no color, no taste, and no smell. All of the different types of radiation travel around our planet, and the universe, at the very same speed. We call this speed “the speed of light,” but it is, in fact, the speed of every type of radiation. Light just happens to be our favorite type.
The only difference between one form of radiation and another is how fast
that radiation vibrates as it travels. Thus the light we use to see differs from the microwaves used to for cooking only in how fast it is vibrating as it travels through space. Because this rate of vibration is the only discernible property of radiation, we symbolize radiation as little, squiggly lines flying around us. This allows us to describe radiation by the distance between peaks and troughs in our squiggly lines. The length from peak to peak or trough to trough is called the “wavelength” of the radiation, and it is the only sure way to distinguish one type of radiation from another. In the case of visible light, these lengths are very, very
small, so they are often described in Nanometers. A nanometer is so short that it takes one billion of them make a meter.