There is a relationship between the size of the soil particles found in a mass of soil and the
amount of moisture soil can store.
Figure depicts laboratory spectroradiometer reflectance of dry silt and sand soils. It shows:
increasing reflectance with increasing wavelength, especially in the visible, near-and middleinfrared
portions of the spectrum.
Incident radiant flux may be reflected from the surface of the sand grains yielding
specular reflectance, or the incident energy may penetrate some distance into the sand
particles.
The energy may then be absorbed by the particle and be scattered or absorbed by other
particles. The void between the soil particles is called the interstitial air space.