- With regard to outdoor light, the angle between the two directions in a plane in which the intensity is equal to a stated percentage of the maximum beam intensity. The percentage is typically 10% for floodlights and 50% for roadway luminaries.

serif"> - The divergence of the sound beam as it travels through a medium. Specifically, the solid angle that contains the main lobe of the beam in the far field.

A measure of the spread of light from a reflectorized light source, a special-shaped lamp with a reflective coating inside the glass bulb to direct the light forward. The beam spread may be very narrow (narrow spot, NSP), very wide (wide flood, WFL), or something in-between (narrow flood, NFL, for example). Examples of "reflectorized light sou [..]

The angle between the two directions in the plane in which the intensity is equal to a given percentage (usually 10 percent) of the maximum beam intensity.

Emission angle

The angle between the two directions in the plane in which the intensity is equal to a given percentage (usually 10 percent) of the maximum beam intensity.

The width of a light beam, expressed in degrees. The beam of light from a reflector-type lamp (PAR, R, ER, or MR) can be thought of as a cone. The beam spread is the angular width of the cone. Common beam spreads are known as spot, narrow, narrow flood, and flood.