Building Utilities 3: Lighting and Illumination

Illumination

defined as the act of illuminating, or supplying light

Lighting

The equipment or fixture used to provide illumination

Intensity

Referred to as luminous intensity described as quantity of visible light that is emitted in unit time per unit solid angle

Luminous flux

Measure of the total perceived power of light

Color of light is measured in [BLANK]

Kelvin (K)

Lower K

warm colored lighting

Higher K

cool colored lighting

Color Rendering Index (CRI)

measurement showing effect of a light source on the color of objects based on a 0 to 100 scale

Correlated Color Temperature (CCT)

A measure of the coolness (red, orange) to warmness (blue-white) appearance of a light; measured in kelvins (K).

Illuminance

Total luminous flux on a surface per unit area; SI Unit is Lux

Glare

A phenomenon caused by extremely bright light sources or by strong brightness contrasts in the visual field

Light

Defined as an artificial source of illumination

Inverse Square Law

the intensity of radiation is inversely proportional to the square of the distance from the source of radiation

Luminescence

light emitted by means other than burning, such as chemical or biochemical action or radiation

Fluorescence

A means of producing light from gaseous discharge

Light travels at what speed?

3.0 x 10^8 m/s (186,000 miles per second)

Absorption

When a composite light such as white, falls on a surface other than black, selective absorption occurs.

Absorptance

The ratio of light absorbed by a material to the light falling upon it

Reflection

the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through

Laws of reflection

1) The angle of incidence equals the angle of reflection.
2) The incident ray, the reflected ray and the normal all lie in the same plane.

specular reflection

a reflection produced by a smooth surface in which the light at an angle equal to the angle of incidence

diffuse reflection

Reflection that occurs when parallel rays of light hit a rough surface and all reflect at different angles

spread reflection

polished surface that is hammered, deeply etched, or engraved, and spreads out any rays it reflects.

Compound reflection

Reflector materials that exhibits all three types of reflection components to varying degree

Transmission

the passage of light through an object. Refracted as it enters the material, but emerges at the same angle that it entered.

Diffusion

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

Refraction

There is a change in speed of light as it travels from one medium to another and there is a bending of the ray of light.

Polarization

the phenomenon in which waves of light or other radiation are restricted in direction of vibration

Interference

The phenomenon of modification in the intensity of light due to redistribution of light energy in the region of superposition of two or more light waves.

diffraction of light waves

Occurs when an object causes a wave to change direction and bend around it

Produces bluish white color; contains mercury vapor use for industrial and outdoor purposes.

Mercury lamp

Contains mercury vapor and other halides to improve efficacy and their color-rendering characteristics. These are lamps used for indoor purposes

Metal Halide (MH) lamp

Lamp that is constructed with two envelopes: an inner envelope (arc tube) made with material that has electric resistance to sodium and an outer envelope to protect the arc tube.

High Pressure Sodium (HPS) lamp

The initial lumens of luminaires will drop by certain percentage after a period of use.

Light Loss Factor

When luminaire collects dirt on its surface the light output is reduced to a certain degree.

Lamp Dirt Depreciation (LDD)

The ratio between the lumen generated from the luminaire and the lumen reaching the work of plane

Coefficient of Utilization (CU)

1 lumen per sq. ft.

Footcandle

Lumen

unit of luminous flux

Lux

1 lumen per sq. m.

Luminosity

the true brightness of an object; lumens per watt

Luminance

The luminous intensity of any surface in a given direction per unit of projected area of the surface, as viewed from the direction.