Abstract

It is known that microwaves with wavelengths ranging from 1 m to 1 mm or with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm) are absorbed by the water vapor in the material. But in contrast to the radiation from infrared (IR) spectral range, where absorption is limited by the surface, microwaves can penetrate into deeper thicknesses of material. This means that the tested materials can be transparent to microwaves and thus the intensity of transmitted radiation will carry information about the amount of moisture in the sample investigated. Therefore, currently, this method is widely used in determining the moisture content in various materials. The analysis carried out in the present chapter shows that this approach can be successfully used not only to control the moisture in solids, but also for studies of atmospheric water vapor.