# Debye Length

From Soft-Matter

## Definition

The Debye length (<math>\kappa ^{-1}</math>), or Debye screening length, is the length scale over which charge carriers screen-out electric fields. One version of this equation when describing this length in a colloidal dispersion (or electrolyte solution) is:

<math> \kappa^{-1} = \sqrt{\frac{\varepsilon_0 \varepsilon_r k T}{2 N_A e^2 I}}</math>

where *I* is the ionic strength of the electrolyte, ε_{0} is the permittivity of free space, ε_{r} is the dielectric constant, *k* is the Boltzmann constant, *T* is the absolute temperature in kelvins, *N _{A}* is Avogadro's number, and

*e*is the elementary charge.

For more information on Peter Debye's original acoustic experiments, go to Electokinetics: Electroacoutic measurements.

## References

- http://en.wikipedia.org/wiki/Debye_length#Debye_length_in_an_electrolyte
- R. Jones, "Soft Condensed Matter," Oxford University Press Inc., New York (2002).