Lighting A to Z

GlossaryAbsorption Conversion of light to heat by interactionwith matter.Accent Lighting Directional lighting to emphasize aparticular object or to draw attention to the field of view.Alternating Current (AC) Flow of electricity which cyclesof alternates direction many times per second. The number ofcycles per second is referred to as frequency. The most commonfrequency used in this country is 60 Hertz (cycles per second).Amalgam A mixture of mercury and other metals used inCompact Fluorescent lamps to allow the lamps to have a stablelight output over a wide range of temperatures and burningpositions. The amalgam causes the lamp to have a 60 secondwarm-up time.Ambient Lighting General lighting, or lighting ofthe surrounding area.American National Standards Institute (ANSI)A consensus organization which coordinates voluntarystandards for the physical, electrical, and performancecharacteristics of lamps, ballasts, luminaires, and other lightingand electrical equipment.Amperes (amps or A) The unit of measurement of electriccurrent. The is current related to voltage and power as follows:Current (amps) = Power (watts)/Voltage (volts).Arc Discharge (in gas or vapor) Electric dischargethat produces light without a filament.Average Illuminance (E av)) Over a surface. Illuminanceaveraged over the specified surface.Ballast Device used with fluorescent and HID lamps to providenecessary starting voltage and limit the current duringoperation.Base The end of the lamp that inserts into lamp socket.Beam Spread The angle over which the intensity of thebeam drops to 50% of its peak intensity. Measured in degrees.Brightness A visual sensation that describes how muchlight an area appears to emit. There are no units of measure forbrightness; its measurement is relative. In other words, moreor less bright.Lighting A–Z 43