Light_Vocabulary

GLOSSARY

-Arc Length In High Intensity Discharge lamps this is the distance between the electrode tips, which represents the physical length of the electrical discharge. -Ballast An auxiliary piece of equipment required to start and to properly control the flow of current to gas discharge light sources such as fluorescent and high intensity discharge (HID) lamps. Typically, magnetic ballasts (also called electromagnetic ballasts) contain copper windings on an iron core while electronic ballasts are smaller and more efficient and contain electronic components. - Bayonet A style of bulb base which uses keyways instead of threads to connect the bulb to the fixture base. The bulb is locked in place by pushing it down and turning it clockwise. - Blackbody A hot body with an incandescent black surface at a certain temperature used as a standard for comparison. Note that a black surface is the best radiator possible. A tungsten filament will emit slightly less radiation than a blackbody at the same temperature.

- Cathode Metal filaments that emit electrons in a fluorescent lamp. Negatively charged free electrons emitted by the cathode are attracted to the positive electrode (anode), creating an electric current between the electrodes.

- Windings of copper or aluminum wire surrounding the steel core in ballast. Also refers to the entire assembly comprising the inductor or transformer.
 * Coil**

- Any metal terminal emitting or collecting charged particles, typically inside the chamber of a gas discharge lamp. In a fluorescent lamp, the electrodes are typically metal filaments coated with special powders called emission mix. Negatively charged free electrons emitted by one electrode are attracted to the positive electrode (anode), creating an electric current and arc between electrodes.
 * Electrode**

- -
 * Glare**: direct glare is caused by light coming directly to the eye from a light source. Indirect glare is light reflected from a surface in the direction of the eye. Both can harm vision and cause visual discomfort or disability.
 * High Pressure Sodium Lamp**: a high intensity discharge ([|HID]) light bulb that illuminates by radiation from sodium vapor producing a yellowish color rendering, when supplied with electricity from a [|ballast]. This type of light bulb is often used in street lights and is available with clear or phosphor coated glass envelopes. Often abbreviated as HPS lamps they are considered to be quite efficient producing about 100 [|lumens]/[|watt].

-
 * Infrared Radiation**: a type of invisible radiation for which the wavelengths are longer and frequency lower than those for visible radiation.

-
 * Opaque**: a term that describes a material that does //**not**// transmit //**any**// visible light. A wooden door, aluminum foil, and bricks are all examples of opaque materials.

-
 * Rapid Start**: a fluorescent system that does not require starters and takes 1 to 2 seconds to emit light. The ballast preheats the electrodes within the [|fluorescent lamp] and initiates the arc without a starter or the application of high voltage.

-
 * Security Lighting**: lighting that is used to protect people and property from criminal activity. When properly employed, security lighting eliminates shadows near buildings and provides even landscape illumination for pedestrian safety.

-
 * Snoot**: a protruding hollow cone of opaque material that provides a high cut-off angle for certain types of track fixtures, landscape lights, or spotlights. A snoot focuses light into a small area and is often used in art gallery lighting, landscape lighting, or theater lighting

- A long, recessed lighting unit, usually installed in an opening in the ceiling. -
 * Troffer**