A good resource would be the American Association of Physicists in Medicine website (
www.aapm.org).
I am a practicing clinical
medical physicist. Choppy did a good job giving some examples of the sorts of things a clinical physicist does. Your role in the workflow of patient care will differ depending on whether you pursue a career in diagnostic physics (dealing with medical imaging used for diagnosing disease), therapeutic physics (dealing with equipment and techniques for treating disease) or nuclear medicine physics (can be used for either).
Personally, I am a therapy physicist and can offer some perspective on the role of a therapy physicist in a radiation oncology department. Typically the physicist is considered to be the technical expert for essentially everything in the department. This includes the radiation-producing equipment and their safe operating conditions as well as procedural issues and how they relate to patient safety. Really you should think of the physicist as the person responsible for ensuring the safety of everyone involved in patient care.
The physician prescribes a course of therapy to a patient and as the physicist it is your responsibility to make sure that each patient is treated correctly and that both the patient and staff are safe.
You will need to be knowledgeable about the safe operation of complicated equipment such as linear accelerators and computed tomography scanners. You will need to understand the inner workings of complex computer systems and algorithms which deal with radiation transport and radiation dose calculation. You will need to be somewhat good with your hands and a bit imaginative in case you are asked to build custom equipment for patients with special needs. You will need to be able to think and respond to problems under working conditions that are sometimes stressful and rushed. You will need to have good bedside manner and be empathetic with patients for those times when you are involved in their education or involved with their treatment in a more hands-on way.
You will have to often work long hours including occasional weekends and you will probably not get recognition from most people for those cases where you go above and beyond to keep the department running (after all, most everyone else will show up after you do in the morning and leave before you do at night...they don't know what you do after they leave). You might feel stretched quite thin at times.
You will typically be the first person anyone in the department goes to when there is a problem or something to be answered that has a technical procedural basis. You will often be asked questions that you simply don't know the answer to but you will have to use your best judgment and past experiences to answer as best as possible and always with the patient's best interest at heart.
You will need to be able to communicate clearly with medical professionals including doctors (radiologists, radiation oncologists, medical oncologists, etc..) and other physicists, some holding Ph.D.'s and some holding M.S.'s. Other staff include nurses, therapists, dosimetrists, medical residents, medical students, therapy students, etc..
Medical physics is not like other branches of physics. Medicine, especially radiation oncology, is very evidence based and as such you will find yourself doing the same things over and over and over again because those are the things which have proven to be effective. Of course the field is constantly evolving, but for the most part you will be doing the same quality assurance procedures every day, week, month, year...you will be checking treatment charts in much the same way every week and reviewing treatment plans that all look very similar after you've done it for a while. You will be filling out the same forms and going over the same paperwork time and time again.
However, through all of this you must always be doing your work with a skeptical eye and always be looking for mistakes and problems. It is your job to catch them, fix them, and prevent them from happening again. There may be only one significant mistake in 500 treatment plans that you review and you better damn well be able to catch it.
There are some distinct advantages to being a
medical physicist should you pursue it. You will have a career you feel good about and that is secure. You can go home at night feeling good about the work that you did that day. The pay is very good (feel free to Google "AAPM Salary Survey") and you do have some degree of autonomy in your work. I would recommend shadowing a physicist for a while before deciding on pursuing it and making sure it is right for you.