i.e., .......................(2.81c)

Thus we find that the normal component of the flux density vector D is discontinuous across an interface by an amount of discontinuity equal to the surface charge density at the interface.

Example

Two further illustrate these points; let us consider an example, which involves the refraction of D or E at a charge free dielectric interface as shown in the figure 2.18.

Using the relationships we have just derived, we can write

.......................(2.82a)

.......................(2.82b)

In terms of flux density vectors,

.......................(2.83a)