For and , the function hasIt is strictly increasing, so the retarded-time equation has at most one solution.
Articles by others on the same topic
Retarded time is a concept used in physics, particularly in the fields of electromagnetism and wave propagation, to account for the time delay that occurs when a signal travels through space. It is important in scenarios where the effects of changes in a source (like an oscillating charge) are not felt instantaneously at a distant point due to the finite speed of light (or other waves).