
7
INTERFERENCE
This chapter and the next both address the coherent addition of light waves. Maxwell’s equa-
tions by themselves are linear in the eld parameters, E, D, B, and H. Provided that we are
working with linear materials, in which the relationships between D and E, and between B
and H, are linear, D = n
2
0
E, and B = μ
0
H, the resulting wave equation (1.14) is also linear.
This linearity means that the principle of linear superposition holds; the product of a scalar
and any solution to the differential equations is also a solution, and the sum of any solutions is
a solution. In Chapter 14, we will explore some situations where D is not linearly ...