Request a grade of "Incomplete" by filling out a form that is available in the Physics Department Office and also from many other places around campus. That form has you promise to do the exam sometime before 30 days into the following semester and permits me to turn in a grade of "I" instead of the "F" that you would probably get without the final exam score. Once you take the final, the grade is changed from "I" to the one that you have earned.