CRITICAL OPALESCENCE: CONCEPT AND IMPORTANCE

The phenomenon of critical opalescence is associated with a continuous or second order phase transition. Originally, it was reported by Thomas Andrews in 1869 for the liquid-gas transition in carbon-di-oxide. In this phenomenon, a substance appears milky or opaque due to significant increase in light scattering, particularly, near its critical point. This occurs because the density of the substance fluctuates greatly at the critical point, where the liquid and gas phases become very difficult to distinguish. In this communication, we will try to formulate a concept of critical opalescence and discuss its importance, particularly, in the field of phase transition, from the basic knowledge of statistical mechanics, which explains the behaviour of systems with a large number of particles.