Is it permissible for a trainee doctor to observe the physician while treating patients and to inquire about ambiguous cases when no patient is present?

There is no legal impediment to staying with the doctor and observing how he treats patients in order to benefit, as long as this does not hinder the student's work or consume his time, or if there is another legal impediment. This action is commendable for whoever wishes to learn, especially since medicine is among the communal obligations (fard kifaya), and some scholars may even prefer it over individual obligations (fard ayn) due to its widespread benefit.