Diffraction of water waves at a slit and at an obstacle

In the experiment P1.6.5.3, a straight wave front strikes slits and obstacles of various widths. A slit which has a width of less than the wavelength acts like a point-shaped exciter for circular waves. If the slit width is significantly greater than the wavelength, the straight waves pass the slit essentially unaltered. Weaker, circular waves only propagate in the shadow zones behind the edges. When the slit widths are close to the wavelength, a clear diffraction pattern is formed with a broad main maximum flanked by lateral secondary maxima. When the waves strike an obstacle, the two edges of the obstacle act like excitation centers for circular waves. The resulting diffraction pattern depends greatly on the width of the obstacle.