Critical opalescence is a phenomenon which arises in the region of a continuous, or second-order, phase transition. Originally reported by Thomas Andrews in 1869 for the liquid-gas transition in carbon dioxide, many other examples have been discovered since. The phenomenon is most commonly demonstrated in binary fluid mixtures, such as methanol and cyclohexane. As the critical point is approached, the sizes of the gas and liquid region begin to fluctuate over increasingly large length scales. As the density fluctuations become of a size comparable to the wavelength of light, the light is scattered and causes the normally transparent liquid to appear cloudy. Tellingly, the opalescence does not diminish as one gets closer to the critical point, where the largest fluctuations can reach even centimetre proportions, confirming the physical relevance of smaller fluctuations.
- Wikipedia, Critical opalescenece (http://en.wikipedia.org/wiki/Critical_opalescence)
물리화학 공부하다가 초임계유체(supercritical fluid)는 상(Phase)의 경계면을 구분할 수 없게 사라진다고 나와있어서 실제로는 어떤 모습인가 궁금해서 찾아보았다.