Many students struggle to understand that a light ray is (most often) just a model used to depict the behaviour of light.
The following worksheets may help to identify whether students hold this particular misconception.
For more information, see the University of York BEST website.
Resources to Address This
Reflection of light (5-11)
Ref - SPT HS01 PN07
When thinking about ray diagrams, it is important that you remember that they are a model: they predict what will happen, but do not show a photo-realistic imitation of the phenomenon.
Sometimes it helps to start with all the light from a source and then reduce the diagram to a significant few rays.View Resource
Ray diagrams model events (11-14)
Ref - SPT Li02 TL02
The first point to make clear to pupils is that a ray diagram is a model of a real process and drawing one involves making various simplifications.
Making these kinds of simplifications may seem obvious to the experienced teacher, but they are unlikely to be so obvious to pupils.View Resource
Interpreting ray diagrams (14-16)
Ref - SPT Ra01 TL12
A ray diagram is a tool used by physicists to explain or predict the behaviour of beams of light as they pass through objects such as glass blocks or lenses.
The distinction between real and theoretical worlds in relation to light is important. It is worth emphasising in your teaching:View Resource
Experiments with a fan of rays (11-16)
Ref - Practical Physics; Light and optics; Investigations with ray streaks
Students should begin to realize that the light travels in straight lines and that an object is seen when light enters the eye. A lens bends light rays so that the rays pass through an image point. We think we see the object at the image point.View Resource
The following studies have documented this misconception:
- Grusche, S. () Students’ ideas about prismatic images: teaching experiments for an image-based approach. International Journal of Science Education, https://doi.org/10.1080/09500693.2017.1312625.
- Muñoz-Franco, G.; María Criado, A. and García-Carmon, A. () Investigating Image Formation with a Camera Obscura: A Study in Initial Primary Science Teacher Education. Research in science education, Springer Science+Business Media B.V., part of Springer Nature 2018.
- Andersson, B. and Kärrqvist, C. () How Swedish pupils, aged 12‐15 years, understand light and its properties. European Journal of Science Education, 5 (4),
- Watts, D M. () Student Conceptions of Light: A case study. Physics Education, 20,
- Osbourne, J.; Black, P.; Smith, M. and Meadows, J. () Primary SPACE project - light, Liverpool University Press.
- Ramadas, J. and Driver, R. () Aspects of secondary students' ideas about light, University of Leeds Centre for Studies in Science & Mathematics Education.