Light_Vocabulary

**AC (Alternating Current):** Current which flows in one direction and then the other, alternately. **Accent Lighting**: Directional lighting to emphasize a particular object or draw attention to a display item.

**Adaptation:** The process by which the human eye adjusts to a change in light level.

**Alabaster**: genuine alabaster is a very fine variety of crystalline gypsum (hydrous calcium sulfate) found in nature. It is translucent and its color is often white, pearly, or silky colorless but it, more often than not, has subtle reddish-brown bands of iron oxide running through it. It is often used for decorative objects such as light fixtures or figurines. Some light fixtures use faux alabaster, which is usually man-made glass. **Baffle:** in lighting this is usually a grooved surface that deflects and controls the “flow” of light to soften it and minimize reflected glare.

**Ballast:** an electrical device used with fluorescent and HID (high intensity discharge) lamps (light bulbs) to supply sufficient voltage to start and operate the lamp but then to limit the current during operation

**Bollard:** an outdoor luminaire that is a short (usually about 2-4 feet in height) but very sturdy vertical post with the light source located at or near the top. Bollards are typically used to light walkways in commercial settings.

**Cave Effect:** an unwanted consequence often associated with parabolic troffers, the cave effect is created when the light fixtures in a room apply no direct light to the upper part of walls due to an extreme cut-off angle

**Circline:** a type of fluorescent lamp that is made up of a circular tube of glass; when placed in a light fixture the ballast that powers this type of lamp is usually located in the center of the circline lamp

**Daylight Harvesting:** Lighting design for building interiors that makes of daylight as a way of reducing energy consumption. Floodlight: a broad-beamed high intensity artificial light source  **Glare:** direct glare is caused by light coming directly to the eye from a light source. Indirect glare is light reflected from a surface in the direction of the eye. Both can harm vision and cause visual discomfort or disability.

**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.


 * Wall Grazing:** a lighting term that refers to the dramatic highlight and shadow effects on uneven surfaces such as draperies, stone, and brick. Grazing creates easily distinguishable high and low levels of light on the irregular surface.