ABSTRACT
This chapter provides a brief revision of the main features of the electromagnetic spectrum, and some fundamental quantities that are employed to quantify the radiation. It describes the blackbody radiation for later reference, starting with the radiative properties of a blackbody, and formulating the properties of thermal radiation, consisting of the spectral distribution of number of photons and their energy. The chapter examines the main aspects of the solar spectrum, which is the energy source that utilizes for the production of useful energy, and how it relates to the idealized blackbody spectrum. The blackbody spectrum is a very important tool for a number of aspects of devices, physics and chemistry. It describes thermal radiation, which is the radiation of hot objects such as the sun, a hot filament or incandescent materials in general. Incandescent light sources allow our visual system to easily distinguish the colors of objects.
