General properties of waves — Describe

How is a ripple tank used to demonstrate (a) reflection, (b) refraction, (c) diffraction through a gap, and (d) diffraction at an edge?

(a) Reflection: straight water waves striking a plane barrier reflect off it with the angle of reflection equal to the angle of incidence. (b) Refraction: waves passing from deep to shallow water (across a boundary formed by a submerged plate) slow down and their wavelength decreases; if they meet the boundary at an angle they also change direction. (c) Diffraction through a gap: waves passing through a narrow gap in a barrier spread out into the region beyond, especially when the gap width is similar to the wavelength. (d) Diffraction at an edge: waves passing the edge of a barrier bend round into the shadow region behind it.