The starting point of the treatment of geometrical optics is the very powerful. Principle of Fermat (1657). The path followed by a light ray between two points is the one that takes the least amount ...The starting point of the treatment of geometrical optics is the very powerful. Principle of Fermat (1657). The path followed by a light ray between two points is the one that takes the least amount of time.
The discussion has focussed on systems having only a single function y(x) such that the functional is an extremum. It is more common to have a functional that is dependent upon several independent v...The discussion has focussed on systems having only a single function y(x) such that the functional is an extremum. It is more common to have a functional that is dependent upon several independent variables f[y1(x),y′1(x),y2(x),y′2(x),....;x].
