The American Institute of Physics (AIP) keeps statistics on employment, schooling, salaries, etc., for physics and astronomy majors. These are broken down by degree. About 45% of BS students go directly into employment. Another 35% go into physics graduate programs. And 20% get schooling in other areas. BS physics & astronomy students have roughly a 95% placement in some type of employment or graduate program. The trends over time are given here.
Nationally, about 50% of students who graduated with a BS in physics work in the private sector, 70% of these in science and technology. The other 50% work in high schools, colleges, the military, the government, national labs, etc. Typical salaries in the private sector in 2004 were $35,000 - $55,000. High school teachers earned around $35,000. It should be kept in mind that new science initiatives in high-schools around the country are leading to a shortage of qualified physics teachers, which will also increase the salaries. See the full statistics and graphs here.
Physics majors who want to go onto medical school tend to do much better than life-science majors on the entrance exams (the MCAT). In 2003, physics majors had the third highest score out of 13 majors. Biomedical-engineering and economics were the only majors that scored slightly above physics majors. See the data here.
Most students (90%) who go on to graduate school enter PhD programs, though some of these leave with an MS. Masters programs typically take 2 years. About 30% of MS students then go onto PhD programs in physics. About 15% get schooling in other areas. And about 50% take employment, with salaries in the private sector in 2004 ranging from $45,000 to $70,000. The statistics on Masters students are given here.
As mentioned above, the majority of students going into graduate school go into a physics PhD program, wherein tuition is free and you earn a stipend. A PhD typically takes 5-6 years; 2 years of classes and 3-4 years of research. After getting a PhD, the typical path is to then take a post-doctoral research position for 2 or more years. These have salaries that range from $30,000 to $90,000. About two-thirds of recent graduates go into some kind of academic position (post-doc, permanent, or temporary), about 20% into government positions, and 15% into industry. Salaries of people with physics PhDs (not just recent graduates) ranges from $45,000 for some faculty positions, to $100,000 for researchers at national labs, to more than $130,000 for medical physics positions at hospitals. These statistics are given here.