Some students believe shadows are a reflection of an object and therefore always expect the shape of a shadow to be the same shape as the object.
For example, they might consider it 'a dark reflection'.
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
Introducing light sources and shadows (5-11)
Ref - SPT HS01 TA08
Confirm how shadows are formed and how they change in size as the distances between lamp, object and screen change.View Resource
Ray diagrams (11-14)
Ref - SPT Li02 PN01
One of the distinctive and interesting features of teaching and learning about light is the way in which ideas and explanations are represented with ray diagrams. Make sure you show how the diagram is constructed and that we are only including two particular rays (but you could start with rays in every direction from the source).View Resource
Shadows and rays on a screen (11-16)
Ref - Practical Physics; Light & Optics;Intro to rays and images
Varying the distances between lamp, object and screen show how the shadow changes size.View Resource
The following studies have documented this misconception:
- Wenham, E. J. and Guesne, E. () The Place of Optics in Physics Teaching - Children's Ideas about Light. New Trends in Physics Teaching, IV
- Feher, E. and Rice, K. () Shadows and Anti-Images: Children’s Conceptions of Light and Vision II. Science Education, 72 (5)
- 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.