The plot thickens. Elementary, my dear Watson. The game is afoot. The mystery will be solved. This machine uses rays of infrared light to pass through an object.
Every object has a characteristic spectra in the infrared spectrum.
The difference in soil lies in the organic materials, which are a small percentage of the whole. The bulk of soil is made of inorganic material, like sand. The IR is used to identify the spectra of the organic material in the soil. The IR uses two methods to analyze an object and obtain a spectra. The first is reflection where the infrared light reflects off of an object to create a pattern or spectra.