The study reported in this talk is a survey (n=236) that examines how upper secondary students in Norway (18-19 years old) come to terms with the main idea of quantum physics as contrasted to classical mechanics. Two concepts were chosen as indicators, the concept of modelling the atom and the concept of wave-particle duality. The main conclusion is that most students seem to be locked into the classical worldview where material particles have definite locations and moves along definite tracks. Very few of the students demonstrates, through the items given, that they have been able to grasp that, on this scale, the phenomena can not be understood through the lenses of classical mechanics. This paper goes into details on the part of the study concerning atomic models, but only summarises the part on wave-particle duality. A paper to be published in the Int. J. of Sci. Edu. presents this latter part in more detail.