  In this paper, we discuss how the concepts of Hamiltonian optics are
internally connected to the scalar wave theory of light rays. It is shown that
the solutions of the reduced wave equation are similar to Huygen's wavelets,
and they can be used to understand Snell's law of refraction. This model can
also be used to derive the coefficient of reflection consistent with Fresnel's
equation for $s$-polarized light.
