Light_Vocabulary

__Arc__: Intense luminous discharge formed by the passage of electric current in a gaseous medium across a space between electrodes.

__Baffle:__ in lighting this is usually a grooved surface that deflects and controls the “flow” of light to soften it and minimize reflected glare. Baffle trims (sometimes called step baffle trims or stepped baffle trims), made of plastic or metal, are often integral parts of recessed downlights. They are often colored a flat black to absorb some of the light but can have other finishes such as flat white, brushed copper, or brushed nickel.

__ANSI Ballast Type__: Ballast type used to operate lamp in accordance with ASNI standard.

__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.

__Ballast Hum__: Sound generated by the vibration of laminations in the iron core of the transformer or inductor present in the ballast.

__Basket Troffer__: a troffer whose light sources are concealed by curved opaque shielding called "baskets", which are often perforated with a pattern of small holes.

__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.

__Bi-Pin__: Any base with two metal pins for electrical contact. This is the typical base for a fluorescent tube of 1 to 4 feet in length. It consists of 2 prong contacts which connect into the fixture. Medium bi-pins are used with type T-8 and T-12 tubular fluorescent lamps, and miniature bi-pins are used for tubular T-5 fluorescent lamps.

__Beam Angle__: The angular dimension of the cone of light from reflectorized lamps 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.

__Brick Light__: a light fixture (usually the size of a brick) that can be recessed in a brick wall with its face parallel to the surface of the brick surface in order to light a walkway, a step, a landing, or a path

__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.

__Center Beam Candlepower (CBCP)__: Refers to the luminous intensity at the center of the beam of a blown or pressed reflector lamp (such as a PAR lamp). Measured in candelas.

__Chandelier__: a chandelier is often the focal point of the dining room. As such it should be hung about 30 inches above the tabletop and should be at least 6 inches narrower than the table on each side.

__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")

__Lumens__: A measure of the luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides about 840 lumens.

__Luminaire__: a light fixture. This should not be confused with the term, luminary, which is a small open paper bag, sometimes with a design on it, containing a lit votive candle set in sand. Luminaries are often used to line outdoor walkways to provide a festive mood to a setting and a certain level of safety. In Mexico and the southwest USA, the terms, luminary and luminaries, become luminaria and luminarias. The term, luminary, can also refer to a person who has attained eminence in his/her field or is an inspiration to others.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__PAR Lamp__: PAR is an acronym for a parabolic aluminized reflector.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__Photometry__: The measurement of light and related quantitie

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__Scotopic__: Vision where the rods of the retina are exclusively responsible for seeing, typically like the light levels in the countryside on a moonless, starlit night

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__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.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__Troffer__: a large recessed ceiling luminaire (light fixture) that often uses 1-4 T5, T8, or T12 fluorescent lamps (light bulbs), usually measures 24in by 48in or 24in by 24in, and is usually installed with the opening flush with the ceiling

<span style="font-family: 'Comic Sans MS',cursive; font-size: 15px;">__Voltage__: the difference in electrical charge between two points in a circuit expressed in volts; the electric pressure that exists between two points and is capable of producing a flow of current when a closed circuit is connected between the two points; the rate at which energy is drawn from a source that produces a flow of electricity in a circuit; synonyms: electrical potential, electromotive force, EMF; Formulae: volts = amps x ohms, V = I x R, voltage = electrical current x electrical resistance.