How is the physics department in Northwestern? How strong is the physics program(BS) in Northwestern?
No direct information, but USNWR ranks it #26 for its PhD program. You can view it as a ranking of the research reputation of the department (or its faculty). It may or may not imply much for undergraduate experience.
Among major private schools, high ranked Physics departments are in MIT, CalTech, Harvard, Stanford, Princeton, Cornell, Chicago, and Columbia.
If you are looking for strong science program, not just physics, consider adding ISP (integrated science program).
Physics is one of the areas NU is strategically focused on ramping up on - they recently hired a physicist from Harvard and in the process of hiring several more…
http://www.northwestern.edu/newscenter/stories/2015/11/physicist-gerald-gabrielse-to-join-northwestern-.html
http://cfp.physics.northwestern.edu/
http://www.northwestern.edu/fm/projects/our_projects/evanston/mudd-hall-renovation-and-expansion.html