Abstract

Looking back over the past 1000 years, we notice that infrared (IR) radiation itself was unknown until 200 years ago when Herschel’s experiment with a thermometer was first reported. Herschel built a crude monochromator that used a thermometer as a detector so that he could measure the distribution of energy in sunlight [1]. Following the works of Kirchhoff, Stefan, Boltzmann, Wien, and Rayleigh, Max Planck culminated the effort with the well-known Planck’s law.