All physical models have a range of validity where models are designed to obtain a simplified description of some physical mechanism under certain circumstances. If these assumptions are incorrect, the solution of the model might be wrong. Typical examples for physical assumptions are listed below.
Several measures might be taken in order to avoid problems with physical models becoming invalid. In most cases the model is replaced by a refined and perhaps more elaborate or detailed model with extended range of validity. Sometimes it is possible to use refined models only in regions where extended parameter ranges are required.