Stokes relations arise by visualizing the rays running backwards in time, so that there are two incident waves of
amplitudes and . A portion of is reflected and a portion transmitted at the interface. Let and be the coefficients for the wave incident from below. The reflected portion is then and the
transmitted portion is . Similarly, the incoming wave of amplitude splits into waves of amplitudes
and . It must follow that
Therefore, the Stokes relations are obtained as
and
© 1996-2007 Eric W. Weisstein
