Two very small, coherent sources are separated by \(d=2 \lambda\), where \(\lambda\) is the wavelength of the circular waves created by each source.

(a) Use Huygens' principle to construct a dozen wavefronts from each source, six troughs and six crests. Mark antinodes with blue lines and mark nodes with red lines, starting each line at least two wavelengths from either source.

(b) Repeat for the case when the two sources are not coherent, so that waves from one source are exactly one-half wavelength out of phase with waves from the other.

(c) Compare your diagrams. Are the original antinodes still antinodes? Are the original nodes still nodes?