How can we obtain the applied field strength? When performing electrophoretic light scattering (ELS) measurements, the sample is exposed to an externally applied electric field, and we observe the extra movement that the particles undergo as a result of the applied field with the changes in the phase difference between the un-scattered reference laser beam and the scattering from the particles. The electrophoretic mobility µ is the particle velocity v divided by the electric field strength E, where the field strength is the applied voltage over the distance between the electrodes [typically ...