Huygen's principle: plane waves

This app calculates the interference pattern produced by a line of point sources that radiate 2-D waves with the same amplitude and frequency. The linear density of point sources is specified as $n$ sources/cm. The sources radiate with a phase that depends on the position of the sources. The phase is $\Delta\phi y$ where $\Delta\phi$the phase shift per centimeter and $y$ is the position of the source.

If $\lambda$ is much smaller than the spacing between the sources (for instance: $n=$ 1, $\lambda=$ 0.2), a complex periodic interference pattern is observed. However, if $\lambda$ is mcuh larger than the spacing between the sources (for instance: $n=$ 3, $\lambda=$ 1), the resulting interference pattern is plane waves. The direction of the plane waves depends on the phase differences between the sources.

Red is positive and blue is negative. Black regions have no wave amplitude. The sources are the white dots on the left edge.