Velocity increases with an increase in porosity. It decreases with addition of water in material. Fractures in rocks have a limited effect on propagation of electromagnetic energy. Reducing the frequency too low, may cause the waves to diffuse. The change in wavelength effects the frequency of the wave.
Longer wavelengths have low frequencies and shorter waves have high frequencies.
The frequency of a wave measures the amount of times a motion repeats itself in a given time interval. The wavelength is measured in nm from crest to crest of the wave. Ground penetrating radar utilizes radio frequency waves to detect subsurface features. An antenna, which is pulled across the surface of the ground, transmits a signal that penetrates the subsurface. As this signal passes through various layers of sediment, it is reflected back up and received by the antenna.