The intensity of a light in lumens is the product of the brightness in lumens per square inch and the surface area of the sphere with a radius equal to the distance to the source in inches. The function L(D) = 2.2(4\pi D^{2} can be used to represent a particular light’s intensity.
What does the constant 2.2 in L(D) represent?
the intensity of the light
the distance to the source
the brightness of the source
the formula for surface area