Diffusing-wave spectroscopy

<jats:title>Abstract</jats:title> <jats:p>In this chapter we describe a recent development in dynamic light scattering (DLS), which may ultimately have a significant impact on the range of problems that can be addressed and on the types of system that can be studied. We discuss diffusing-wave spectroscopy (DWS), which extends DLS to very highly multiple scattering media. This technique extends the analytic power of DLS to opaque samples such as concentrated suspensions, obviating the need to dilute or index-match. In addition, DWS opens new and exciting possibilities for studying particle dynamics on length scales that are unattainable using conventional methods. We present a summary of the theoretical principles underlying DWS, and discuss its applications, both in extending traditional DLS techniques and in studying new physical phenomena. The development of DWS is still in its relatively early stages, and considerably more work is needed to exploit this technique fully. Our goal here is to provide a comprehensive introduction to the underlying principles, and to provide some examples illustrating the great promise of DWS, in the hope of making further work more productive.</jats:p>