Norsk folkemuseum is absolutely worth the visit, especially in good weather and summer time. In English the museum is called norwegian museum of cultural history. It speaks for itself that this museum is about the cultural herritage in Norway.
The area of this musum is big, it covers a big part of the half island bygdøy, where the musem is located.
The museum contain areas where buildibgs from all times of norwegian history is represented. All from old “stavkirker” (middle age wodden churches), old houses of lafted wood and stabur to old glass stations and buildings of typical homes in Oslo in the 1960s etc. The museum offcourse also contain a main building with items and artifacts at the entrance.
In my opinion thus museum is worth the price of entrance. And can take much of the day, filling it with a good experience. And again conditioning that the weather is nice.