# Dictionary:Frequency effect (FE)

The difference between apparent resistivity measurements (${\textstyle \rho _{a1}}$ and ${\textstyle \rho _{a2}}$) made at two frequencies f1 and f2, divided by the apparent resistivity at one of the frequencies:
${\displaystyle FE={\frac {\rho _{a2}-\rho _{a1}}{\rho _{a1}}}}$..
${\displaystyle M={\frac {FE}{1+FE}}}$.