Section 2 begins by considering the simplest case of a diffraction grating, a single, infinitesimally narrow slit. The purpose of this section is to introduce the primary concepts and approximations used in the later sections. If you are happy accepting Eq. 8 on faith, you can skip Section 2 and begin directly with Section 3.2.

Section 3 studies the phenomenon of *
interference*, which happens in cases where there are more than one
slit. The central result of these notes is the *N*-slit diffraction
pattern (Eq. 17) from this section. From this equation,
one may understand the two slit pattern (*N*=2) as a special case, or
deal with any larger number of slits. In fact, from this one result,
one may also understand the pattern for a single slit of finite width
(Section 4) and for the more complex case of *N*
slits of *finite* width (Section 5).

Thu Sep 13 15:26:14 EDT 2001