
12
RADIOMETRY AND PHOTOMETRY
We have discussed light quantitatively in a few cases, giving consideration in Sections 1.4.4
and 1.5.3 to the quantities irradiance, power and energy. We have also considered the trans-
mission of irradiance and power in the study of polarization in Chapter 6, and thin lms
in Section 7.7. We have briey considered the concept of radiometry in the discussion of
f -number and numerical aperture in Section 4.1. In this chapter, we describe the fundamentals
of the quantitative measurement of light. In one approach, we can think of light as an electro-
magnetic wave, and use the units developed in that eld, Watts, Joules, ...