Light_Vocabulary

**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.

**Beam Angle** The angular dimension of the cone of light from reflectorized lamps (such as __R __ and __PAR __ types) encompassing the central part of the beam out to the angle where the intensity is 50% of maximum. The beam angle sometimes called "beam spread" is often part of the ordering code for the reflectorized lamps. Example: The 50PAR30/HIR/NFL25 is a 50 watt PAR30 narrow flood lamp with a beam angle of 25 degrees (See __<span style="background-color: initial; color: inherit; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">FIELD ANGLE __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">).

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Beam Lumens** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">The total lumens present within the portion of the beam contained in the beam angle

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Blackbody** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">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

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Bollard** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A short, thick post with a light at its top, used for grounds and outdoor walkway lighting.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Bulb** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A loose way of referring to a lamp. "Bulb" refers to the outer glass bulb containing the light source.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Cathode** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Metal filaments that emit electrons in a fluorescent lamp

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**ChromaFit** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A GE brand name for metal halide lamps designed to operate on HPS ballasts, allowing a user to switch from the yellowish color of HPS to the white color of metal halide without changing ballasts. These products are available in both quartz metal halide and ceramic metal halide (CMH) versions.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Coil** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Windings of copper or aluminum wire surrounding the steel core in ballast. Also refers to the entire assembly comprising the inductor or transformer.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Dichroic Reflector (or Filter)** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A reflector (or filter) that reflects one region of the spectrum while allowing the other region(s) to pass through.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Dimmable** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Whether or not the lamp lumens can be varied while maintaining reliability.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Fixture Requirements** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Describes fixture requirements for HID lamps. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">O = Open or Enclosed Fixtures <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">E = Enclosed Fixtures Only <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">S = Lamps operated in a vertical position (Base Up or Down) ±15º, can be used in an open fixture. Lamps burned in any other orientation must be used in "enclosed fixtures only." See additional details in the e-Catalog Help Menu under the HID category.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Flicker** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">The periodic variation in light level caused by AC operation that can lead to strobe effects.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Flood** Used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. ("Flood" as opposed to "spot").

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Glare** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Visual discomfort caused by excessive brightness is called discomfort glare. If task performance is affected it is called disability glare.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Hot Restart Time** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Time it takes for a High Intensity Discharge lamp to reach 90% of light output after going from on to off to on.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Ignitor** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">An electronic device providing a high voltage pulse to initiate an electrical discharge.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Lens** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A transparent or semi-transparent element which controls the distribution of light by redirecting individual rays. Luminaires often have lenses in addition to reflectors.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Mesopic** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Typically referring to nighttime outdoor lighting conditions, the region between PHOTOPIC and SCOTOPIC vision (See <span style="font-family: Arial,Helvetica,san-serif; font-size: 11px;">__<span style="background-color: initial; color: inherit; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">SCOTOPIC __ <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">).

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Open Fixture Rated** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Lamps that are approved for burning in open fixtures (as opposed to enclosed fixtures which have an acrylic lens or plate glass enclosure).

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Reveal** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">GE's product family of incandescent lamps with the element Neodymium added to the glass bulb. Neodymium filters out much of the yellow light produced by ordinary lamps. Less yellow means whites look whiter and colors appear more vibrant in spaces lighted with Reveal lamps.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Sunburn** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Skin reddening and inflammation caused by overexposure to sources containing UV-B and/or UV-C.

<span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Transients** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">High voltage surges through an electrical system caused by lightning strikes to nearby transformers, overhead lines or the ground. May also be caused by switching of motors or compressors, as well as by short circuits or utility system switching. Can lead to premature ballast failure.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> <span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">**Troffer** A long, recessed lighting unit, usually installed in an opening in the ceiling.