The diameter of the rubber stopper is many times larger than the diameter of the metal rod. Wave scattering from the larger object is greater than scattering from the smaller object. This is the same dependence that is predicted for scattering of light from molecules and dust and smoke particles in the atmosphere.

When the diameter of the object that scatters the waves becomes smaller than their wavelength, very little scattering occurs. This means that to measure accurately the position of an object visually, the wavelength of the light must be smaller than the size of the object.