lumen-, lumin-, lum- +

A line on a chart or map connecting points of equal light intensity.

The gradual loss of efficacy (lumen output) of a lamp over time, typically caused by the loss of chemical additives in the lamp and wall darkening in the arc tube.

This can be indicated by a lumen depreciation curve depicting the pattern of decreasing light output.

1. In physics, the SI unit of luminous flux, equal to the amount of light crossing a unit area at a unit distance from a light source of luminous intensity of one candela. Symbol lm.
2. In anatomy, the space inside any tubular structure in the body, e.g., an intestine, artery, or vein.
3. In botany, the cavity within a plant cell wall.

The lumen is based on the spectral sensitivity of the photosensors in the human eyes under high (daytime) light levels.

Photometrically, it is the luminous flux emitted with a solid angle (one steradian [solid angle made at the center of a sphere by an area on the surface of the sphere equal to the square of the sphere's radius]) by a point source having a uniform luminous intensity of one candela [unit of luminous intensity].

1. The condition or quality of emitting or reflecting light.
2. A measure of the brightness of a surface equal to the amount of luminous flux arriving at, passing through, or leaving a unit area of surface.

It is measured in candelas per square meter. A candela is the basic unit of luminous intensity adopted under the Systeme International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin, or the solidification of platinum.

A small candle set inside a paper bag that has been weighted with sand, usually placed outdoors with others as a Christmas decoration; originally, the plural of luminatrium.

1. An eminent or famous person.
2. An object, especially a celestial body, that emits light.
3. Relating to or characterized by light.

1. To emit light by phosphorescence, fluorescence, or bioluminescence.
2. Emission of light from a body as a result of a chemical reaction.

1. Low-temperature emission of light produced especially by physiological processes (as in the firefly), by chemical action, by friction, or by electrical action.
2. Any radiation of light from a body produced by some means other than heat.
3. Any emission of light at temperatures below that required for incandescence.
4. Luminescence can be subdivided into fluorescence and phosphorescence.

1. The emission of light produced by means other than heat (incandescence); such as, phosphorescence, fluorescence, or bioluminescence.
2. The light emitted by luminescence.

1. Generating or giving off light.
2. Producing or conveying light.

1. One who studies the luminescent phenomena in living organisms.
2. One versed in the study of illuminations of manuscripts.

1. A luminescent material that emits radiation by absorbing and then converting a portion of incident energy.
2. An atom or atomic grouping in an organic compound that increases its ability to emit light.

1. The state or quality of being luminous.
2. The energy radiated per second by a celestial body; such as, a star.
3. The visual perception of the extent to which an object emits light.
4. The fact or process of giving off light; the quality of an object that produces light.

1. Full of light; describing the emission of visible radiation.
2. Emitting or reflecting light, with or without accompanying heat.
3. Immensely bright or brightly illuminated.
4. Evaluated on the basis of the visual sensation produced in an observer rather than energy measurements.

The ratio of the radiant energy sensed by the average human eye at a particular wavelength to that received.