In Time Domain Reflectometry (TDR) for soil moisture determination, the apparent dielectric permittivity $\epsilon_b$ of bulk soil is primarily determined by moisture content because:
Options:
(A) The dielectric constant of liquid water ($\approx 80$) is far higher than that of dry soil mineral matrix ($\approx 3-5$) and air ($1$)
(B) Water conducts DC electricity instantaneously
(C) Dry soil has infinite dielectric permittivity
(D) Soil air has a dielectric constant of 80
Answer Key:
A
Step-by-Step Solution & Explanation
Because the relative dielectric permittivity of free water ($\approx 80$ at $20^\circ\text{C}$) vastly exceeds that of dry soil minerals ($3-5$) and air ($1$), the propagation velocity of electromagnetic waves along TDR waveguide rods is governed directly by volumetric water content.