  Physicists and physics students have been studied with respect to the
variation in ways they expound on their topic of research and a physics
problem, respectively. A phenomenographic approach has been employed; six
fourth-year physics students and ten teacher/researcher physicists at various
stages of their careers have been interviewed. Four qualitatively distinct ways
of expounding on physics have been identified, constituting an outcome space
where there is a successive shift towards coherent structure and multiple
referent domains. The interviewed person is characterised as expressing an
'object of knowledge' and the interviewer is characterised as a willing and
active listener who is trying to make sense of it, constituting a 'knowledge
object' out of the ideas, data and personal experience. Pedagogical situations
of analogous character to the interviewer-interviewee discussions are
considered in the light of the analysis, focusing on the affordances for
learning offered by the different forms of exposition.
