The principle of least time

Fundamental to the understanding of optics is the Principle of Least Time, developed by Fermat ( 1650), which says that light will take the path that... 

The principle of least time can also be used to examine reflection. If we perform a similar experiment to that above except that we make one medium reflective at the boundary we will discover that the only paths for which the flight time of the photon is a minimum are those for which the angle of incidence equals the angle of reflection. 

Author of this article has made an attempt to extend further our notions of liquid [11,12]. It is considered now that sublimation is a direct transition from solid (crystalline) state of matter into gas. The author has propounded and substantiated the principle of least time for first-order phase transitions [11,13] it is shown by means of this principle that sublimation goes in two steps through a certain intermediate state in the form of surface film. It is concluded that this film consists of nonstructural liquidlike substance which is a certain antipode of liquid this liquidlike state of matter is named second licjuid [12]. 

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