BU TERMS ON LIGHTING

Zonal Cavity Method/ Lumen Method/ Flux Method

A procedure in lighting design, used to determine the number and types of lamps or luminaries required to provide average level of Illumination on a workplane takes into account both direct and reflected light flux

light loss factor

A Factor used on calculation illuminance after a given period and under given conditions . Also Known as Maintenance Factor.

High Pressure Sodium Lamp

A High Intensity discharge (HID) lamp whose light is produced by radiation from sodium vapor and mercury.

High Power Factor

A ballast with a 0.9 or higher rated power factor, which is achieved by using a capacitor.

Luminaire

A complete lighting unit consisting of one or more lamps together with components which are used to distribute light , to position and protect the lamps to the electric power supply, also called a lighting Fixture

Critical Angle

Angle at which light undergoes total internal reflection

Beam Angle

Angle between two Directions for which the intensity is 50 percent of the maximum intensity, as measured in a plane thru the nominal Beam center line.

Light

Artificial Source of Illumination

Brightness

Attribute of Visual perception in accordance with which a surface appears to emit more or less light.

Brilliance

Clarity, strength , and brightness of a color

Color of Light

Determined by wavelength with red Having the longest wavelength but the lowest frequency, orange, yellow, green , blue , indigo, violet, the shortest wavelength.

Contrast

Difference in Brightness between an object and its background.

Footcandle (FC)

English unit of illumination equal to 1 lumen per square foot. ( Light flux density)

Footlambert

English unit of luminance equal to on 1/Pi candela per square foot.

High Output

A lamp or ballast designed to operate at higher currents (800mA) and produce more light.

Fluorescence

A means of producing light from gaseous discharge.

Room Cavity Ratio (RCR)

A number indicating the proportions of a room Cavity , calculated from the length , width and height of the room.

valence Electron

One of the electrons in the outermost shell of an atom

High Bay

Pertains to the type of lighting in an industrial application where the ceiling is 20 feet or higher.

Glare

Sensation produced by luminance within the visual field that is sufficiently Greater than the luminance to which the eyes are adapted. May cause annoyance discomfort or loss of visual performance or visibility

Point Source

Source of Essentiality zero Dimension, That radiates light uniformly in all directions

Illumination

The Luminous flux density incident on a surface, i. e . the Luminous flux per unit area, usually expressed in lumens per square foot or foot candles , and lumens per square meter.

Absorptance

The Ration of the light absorbed by a material to the light falling upon

Phosphorescence

The action of organic fluorescent material ( rare earth Phosphors) which retains the radiant Energy for short periods of Time

Visible Light

The combination of colors of the visible Spectrum : Red, orange , yellow, green , blue, indigo, violet

Electroluminescence

The conversion of electric energy to light using the passage of Alternation or direct current thru special conductors of solid matter producing visible light.

Illuminance

The density of luminous flux incident on a surface , the quotient of the luminous flux divided by the area of the surface when the latter is uniformly illuminated.

Luminescence

The emission of light Not directly ascribable to incandescence

Luminance

The luminous density of any surface in a given direction per unit of projected area of the surface as viewed from that direction, a directional property of luminous radiation

Intensity

The luminous flux per unit solid angle expressed in lumens per steradians

Luminosity

The ratio of luminous flux to the corresponding radiant flux at a particular wavelength , expressed in Lumens per Watt

Lighting,

The various processes , systems , forms and / equipment used to provide light and illumination

Selective Absorption/ Absorption

This occurs when a composite light such as white , falls on a surface other than black or with,

Lambert

Unit of Luminance equal to 1 / pi candela per square cm.

Candela

Unit of Luminous Intensity, Describing the intensity of a light source in a specific direction, international candle

Lumen

Unit of Luminous flux

Luminescence

When an electric current Is introduced through a gas or solid which is composed of a single Valence Electron., it cause the valence electrons to temporarily rise to a higher level of energy. when the electron resumes its natural state, it radiates enegy in the form of light

Compact Fluorescent

a small fluorescent lamp that is often used as an alternative to incandescent lamp.

IESNA

abbreviation for illuminating Engineering Society of North America

Incandescence

as an element is heated , its molecules become increasingly active until the temperature of the element reaches 500 degrees Celsius

Luminous Intensity

expressed in candle power or candelas or in lumens per steradian luminous flux intensity per unit solid angle in a specific Direction From a Point source of Light.

Indirect Glare

glare produced from a reflective surface

Direct Glare

glare resulting from high luminance or insufficiently shielded light sources in the field of view.

Color Temperature

is a Specification of the color appearance of a light source , relating to the color to a reference source heated to a particular temperature, measured by the thermal, unit kelvin.

Light

is defined as an artificial source of illumination. As "Visually evaluated radiant energy " . A form of Wave energy and Therefore has frequency and wavelength.

luminous efficacy

measure of the effectiveness with which a light source converts electric Power into luminous Flux

Efficacy

metric used to compare light output to energy consumption.

Luminaire Efficiency

ratio of luminous flux ( Lumen ) Emitted by a luminaire to a total flux emitted by the lamp or lamps in the luminaire .

Coefficient if Utilization ( CU )

ratio of luminous flux (Lumens) From a luminaire calculated as received on the work plane to the luminous flux emitted by the luminaire's lamp

Emissivity

ratio of radiant energy emitted by a body to that emitted by a perfect black body . A perfect black body has an emissivity of 1, a perfect reflector an emissivity of 0

Reflectance

ratio of reflected light to incident light

Diffusion

reflected light rays are distributed in all directions with maximum intensity normal to the surface

Color Rendering Index ( CRI)

scale of the effect of a light source on the color appearance of an Object compared to its color appearance under a reference light source.

Photoluminescence

the principle which describes the response of single valence electrons when their atoms are in a gaseous state. The collision of electrons induced by the introduction of electrical current within a confined gas generates an arc discharge, ionizing the vapor molecules

Visual Comfort Probability (VCP)

the rating of a lighting system , expressed as a percent of people who , when viewing from a specified location , and in a specified Direction.

Bioluminescence

Light produced from the oxidation of chemical compounds by Plants and Animals

The Physics of Light

Light provides the stimulus which allows recognition , organization and evaluation of visual information perceived within an environment . Light Defines form, color , creates mood, atmosphere and emphasizes direction and movement.

Fluorescent Lamp

Light source consisting of a tube filled with argon, along with krypton, or other inert gas/s.

Lux (Lx)

A unit of Illumination equal to 1 lumen per square meter

Luminance Meter (brightness Factor)

A visual instrument or photoelectric instrument used to measure luminance

High Intensity Discharge ( HID ) lamp

Generic term describing mercury vapor, metal halide, high pressure sodium, and (Informally) low pressure sodium light sources and luminaires

Discomfort Glare

Glare producing discomfort

Luminaire Dirt Depreciation (LDD)

Multiplicative factor in calculations of illuminance reduced illuminance due to dirt collecting on the Luminaries.

Lamp Lumen Depreciation ( LLD)

Multiplicative factor in calculations of illumination for reduction in the light output of a lamp over a period of time.

Infrared Radiation (IR)

Non visible light characterized by its relation to heat

Ultraviolet Radiation (UV)

Non visible light that can have both harmful and beneficial effects

Natural Phenomena

Radiation of the complete spectrum of light from the sun or stars, the reflection of sunlight off the moon, sky, clouds, earth and bodies of water , lightning, Aurora Borealis, Aurora Australis, and Bioluminescence.

Luminous Flux

Rate flow of light through a surface

Absorption

Ratio of light Absorbed by a material to the light falling upon it.

Luminance Contrast

Relationship between the luminance of an object and the luminance of the immediate background

Intensity

The luminous flux per unit solid angle, expressed in Lumens per Steradian (lm/St) or Candela

Candle Power (CP)

The luminous intensity of a light source , expressed in candelas

Polarization

The phenomenon wherein the waves vibrates only in one plane

Refraction

The processes by which direction of a ray of light changes as the ray passes obliquely from a medium to another

Refraction

The property of a material to change. rection of light at the interface between two different materials, such as air and glass.

Reflection

when light falls upon an opaque material ,

Specular Reflection

when the material has a polished surface, the light will be reflected at an angle equal to the angle of incidence

Diffuse reflection

when the material has an unpolished surface, however reflected light is spread in all directions,