Lump is the general term for an incandescent light source. A number of lamps are available to provide a wide range of wattage at different voltages (Figure

The intensity of a light is determined by the throw, the distance from the light source to the object it is lighting. The intensity is governed by the inverse square law. Once a beam leaves a light, the area illuminated by the beam increases the farther it throws, and the same quantity of light must illuminate a larger area. If the distance between a light and the stage is doubled, the intensity is reduced to one-fourth the original.