# Debye Length

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## Definition

The Debye length ($\kappa ^{-1}$), 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:

$\kappa^{-1} = \sqrt{\frac{\varepsilon_0 \varepsilon_r k T}{2 N_A e^2 I}}$

where I is the ionic strength of the electrolyte, ε0 is the permittivity of free space, εr is the dielectric constant, k is the Boltzmann constant, T is the absolute temperature in kelvins, NA 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.