  The dual nature of matter and radiation and the concept of the structure of
an atom share a number of key conceptual elements from quantum mechanics.
Despite the similarities, we find that the concept of the structure of an atom
is well understood by students, in contrast to the wave-particle duality. The
study analyzes students' comprehension of these two concepts by conducting a
semi-structured focus group interview and questionnaire. Through students'
performance in the questionnaire and their descriptive responses, we find that
the difficulties in their learning and understandings reflect the treatment of
the respective topic in the curriculum. The introduction of the structure of an
atom is early and repeated, whereas the dual nature of matter and radiation is
introduced late and abruptly. Based on our findings, we propose reforms in the
present curriculum that are necessary for an improved way of introducing the
concept of modern physics, like wave particle duality, to Indian students.
