We will hang it above the water surface on the old wooden rod, with two nails driven into it. With vertical vibrations of the rod with a period T, the nails, simultaneously touching the water at points O1 and O2, cause periodic displacements of water particles in them. As a result, waves from two sources spread over the water surface. When these waves are superimposed on the water surface, a stable oscillation pattern is formed, which is called interference.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.