BU Part 3.2

Light

A visually evaluated radiant energy that permits us to see

1. General Lighting

2. Local and Supplementary

3. Combined General and Local

Three Methods of Illumination:

Incandescent Lamps

1. Reflector Lamp

2. Interference (Dichroic) Filters

3. Low-Voltage Lamp

4. Krypton Gas

5. Energy Saving Lamp

6. Tungsten-Halogen (Quartz) Lamp

Fluorescent Lamp

1. Preheat Lamp

2. Rapid-Start Lamp

3. Instant-Start Fluorescent Lamp

4. Cold Cathode Tube

Special Fluorescent Lamp

1. “U” Shaped Lamp

2. Reflector and Aperture Lamp

3. Energy Conserving Lamps

Accent Light

Directional lighting to emphasize a particular object or draw attention to a part of the field of view.

Altitude

Angular distance between the vertical plane containing the sun and the plane of the meridian.

Baffle

A single opaque or translucent element to shield a source from direct view at certain angles or to absorb unwanted Light.

Ballast

Device used with electric discharge lamp to obtain the necessary circuit conditions for starting and operating.

Black Light

Popular term for ultraviolet energy near the visible spectrum

Candela

The unit of luminous intensity

Candela Power

Luminous intensity expressed in candelas.

Clerestory

Part of a building rising clear of the roofs and whose walls contain windows for lighting the interior.

Cold-Cathode Lamp

Electric discharge lamp of the glow discharge type.

Cornice Lighting

Lighting by means of light sources shielded by a plane parallel to the wall and attached to the ceiling that distribute light over the wall.

Cove Lighting

Lighting by means of sources shielded by a ledge or horizontal recess that distribute light over the ceiling and upper wall.

Diffuser

Device to redirect or scatter the light from a source

Direct Lighting

Lighting by luminaries distributing 90 to 100% of the emitted light in the direction

Fenestration

Any opening or arrangement of openings (normally filled with media for control) for the admission of daylight.

Flush-Mounted/Recessed

Luminaire mounted above the ceiling with the opening of the luminaire flush with surface of ceiling.

Foot candle

The unit of illumination. The illumination on a surface 1 sq. ft. in area on  which there is a uniformly distributed flux of 1 lumen.

Foot Lambert

Unit of luminance; the luminance of a perfectly diffusing surface emitting or reflecting light at the rate of 1 lumen per sq. ft.

General Diffuse Lighting

Lighting by luminaries distributing 40 to 60% of the emitted light downward and the balance upward and horizontally.

Indirect Lighting

Lighting by luminaries distributing 90 to 100% of the omitted light upward.

Infrared Radiation

Radiant energy within the wavelength range 770 to 10 to the 6 power nanometers.

Louver

Series of baffles used to shield a source from view at certain angles.

Lumen

The unit of luminous flux.

Luminaire

Complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light

Luminous Flux

The time rate of flow of light.

Polarization

Process by which the transverse vibration of light waves are oriented in a specific plane.

Reflection

Process by which the incident flux leaves a surface or medium from the incident side

Refraction

Process by which the direction of a ray of light changes as it passes obliquely

Filament

Used is tungsten. May be a straight wire, a coil, or coiled coil.

Lead-In-Wires

Made of copper from base to stem press and nickel from stem press to filament

Bulb

Soft glass is used — To withstand higher & for protection wheather

Lamp Lumen Depreciation

Multiplicative factor in calculations of illumination for reduction in light output of a lamp

Luminescence

When an electric current is introduced through a gas or solid which is composed of a single valence

Photoluminescence or Gaseous Discharge

Describes the response of single valence of electrons when their atoms are gaseous state.

Mercury Lamps

Mercury vapor & produces bluish white light. Used for industrial and outdoor application

Metal Halide (MH) Lamps

Mercury vapor & other halides to improve to both their efficacy and their color rendering. Used are scandium, sodium oxides, dysprosium. For indoor use

High Pressure Sodium (HPS) Lamps

Xenon a starting gas and an amalgam of sodium and mercury that is partially vaporized when the lamp attains its operating temp.

Short Arc Lamps

Produce high intensity light from a small bulb, resembling a point source — important for critical light beam controls.

Xenon Lamps

Used primarily as spotlight, in projectors and as searchlights

Low Pressure Sodium (LDS)

Produce a monochromatic yellow-wavelength light at 589 nm.

Electrodeless Lamp

Include several new gen. of lamps and promise to be lamps of the future — no electrodes

Electromagnetic

Excite the gas fill in the lamp and consists of magnetic core and coil at lamp’s center

Electroluminescent Lamps

Emit light by direct excitation of phosphor from an alternating current and produce different colors by mixing of phosphors.

Luminous Intensity

Light power in a given direction defined as the luminous flux per unit solid.

Base

Made of brass — Soldered to the center contact and other to the upper rim of base shell

Button Rod

Glass rod supports button