All visual sensations are produced by the relative differences in length, amplitude, and purity of the light waves. At the back of the eye is the retina. The retina is essentially a membrane consisting of three layers of cells. The receptors cells, the rods and the cones, are located in the middle level . Although rods are better than cones in detecting very weak stimuli they are less adept in resolving details of those weak stimuli.
Visual acuity is the term given to the capacity to discern detail.
Up to a point rods and cones function is the same manner. The are biological transducer capable of converting light waves into neural impulses. Like the eye, the ear is more than simply a biological transducer. Sound is a physical phenomenon produced by the fluctuation in air pressure. Sounds are the results of vibrations that cause molecules to move back and forth.