What is light?
Light, or visible light, as it is often called, is what enables vision. In fact, light is the only thing people see; every object we think we see is a result of light that is reflected off the objects and into our eyes – in the absence of light, we would see nothing. Light is an electromagnetic wave, located between infrared and ultraviolet on the electromagnetic spectrum. Although light is on a wave spectrum, at times it mimics the behavior of particles.
Light refers to a small band of frequencies visible to the human eye among the larger electromagnetic (EM) radiation scale. Most EM waves oscillate at a rate that humans are unable to detect visually. This might be compared with a dog whistle with a pitch that human ears cannot hear. In the same way, some animals can see EM frequencies that humans cannot. Bees, for example, see in the ultra-violet (UV) range to pick out patterns in flowers only visible with UV-equipped vision. EM radiation is an electric field with magnetic properties that propagate from one point to another, or radiate outward. EM radiation is a wave with frequency and amplitude. Frequency refers to how many waves pass a stationary point per second, while amplitude measures the height of a wave. Visible light has a wavelength of 400 to 700 nanometers. To put this in perspective, a nanometer is one billionth of a meter (one billionth of 3.281 feet). Light has different properties depending on its amplitude and waveleng
The choice of lighting is one the most important decisions to make when setting up a reef tank. The light fixtures and related equipment are some of the more expensive pieces of equipment both at initial setup up as well as in their contribution to daily operating costs. In addition to being necessary for the photosynthetic organisms we keep in our aquariums, light also provides the visual element of color. From talking to aquarists and perusing the various reef-related bulletin boards, it has been my experience that lighting and color are often a very misunderstood aspect of aquarium keeping. Given that lighting and color are important in the functional and aesthetic elements of reefkeeping, I feel it is important that hobbyists have a good understanding of light and color. The purpose of this series of articles is to provide beginning and intermediate reef aquarists with a comprehensive understanding of lighting concepts and terminology, and the ability to understand and comprehend l
by Lambert Dolphin Human vision is utterly amazing in its ability to receive and process a wealth of information concerning levels of light intensity, colors, motion, and stereoscopic depth of field. However, as wonderful as our eyesight is, we are able to see only electromagnetic waves between 400 and 700 nanometers (4 to 7 x 10-9 meters) in wavelength. Young Isaac Newton in 1666 used a prism to break visible white light down into the rainbow colors of the spectrum giving impetus to the development of what is now the vast science of optics. Discovery of the wave-nature of light soon led to the realization that our universe is permeated with electromagnetic waves ranging in wavelength over at least 16 orders of magnitude–from ultra low frequency radio waves which are tens of kilometers in wavelength to cosmic rays with wave crests and troughs only a millionth of a millionth (10-12) meter apart. Just in our century science has quickly extended the range of the eye for exploration purpo
Light is simply a name for a range of electromagnetic radiation that can be detected by the human eye. What is electromagnetic radiation, then? Electromagnetic radiation has a dual nature as both particles and waves. One way to look at it is as changing electric and magnetic fields which propagate through space, forming an electromagnetic wave. [illustration] This wave has amplitude, which is the brightness of the light, wavelength, which is the color of the light, and an angle at which it is vibrating, called polarization. This was the classical interpretation, crystallized in Maxwell’s Equations, which held sway until Planck, Einstein and others came along with quantum theory. In terms of the modern quantum theory, electromagnetic radiation consists of particles called photons, which are packets (“quanta”) of energy which move at the speed of light. In this particle view of light, the brightness of the light is the number of photons, the color of the light is the energy contained in
