Vladb is correct. You can be a high school teacher of physics with a bachelors but if you want to do physics research or do some sort of engineering for a company, you need a higher-level degree. Unlike engineers, physics majors don't train for a specific job during their undergrad. Consider a physics B.S. a sort of 'liberal science' degree that gives you enough math and science to go on to related fields (physics, engineering, computer science, what-have-you) but you need more training to truly be ready to use it in a job.