This study focuses on elucidating and
explaining reasons for the stability of and interrelationships
between students’ conceptions about Light Propagation
and Visibility of Objects using contextualized questions
across 3 years of secondary schooling from Years 7 to 9. In
a large-scale quantitative study involving 1,233 Korean
students and 1,149 Singaporean students, data were analyzed
from responses to the Light Propagation Diagnostic
Instrument consisting of four pairs of items, each of which
evaluated the same concept in two different problem situations.
Findings show that only about 10–45 % of students
could apply their conceptions of basic optics in contextualized
problem situations giving rise to both stable and
unstable alternative conceptions. Students’ understanding
of Light Propagation concepts compared with Visibility of
Objects concepts was more stable in different problem
situations. The concepts of Light Propagation and Visibility
of Objects were only moderately correlated. School
grade was not a strong predictive variable, but students’
school achievement correlated strongly with their conceptual
understanding in optics. The teaching and learning
approach and education systems in the two countries may
have had some influence on students’ conceptual