Authenticating GEMs with Optics

When teaching the optics unit in grade 10 science, I have noticed that students often struggle with the concept of refraction, both in lab settings and when working with it in theory such as a practice question or test.  Snell’s Law is the question most often left blank on the exam.  I believe the main reason for this is a misconception of what light is and how it travels, what is happening at the interface between two different substances.  Favale and Bondani, (2014), concur, stating about optics that “These misconceptions are widespread and do not depend on the gender, the level, and the age of the students: they seem to depend on some wrong ideas and explanatory models that are not changed by the curricular studies at school. In fact, the same errors are present in groups of students before and after taking optics courses at High School.”  That’s a goal I have as I go through another optics unit this semester; I plan to utilize a T-GEM inquiry approach to help students work through this difficult concept.

PhET has many useful simulations in the various fields of science, and there is a particularly good one for refraction called “Bending Light” which can be found at https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html.   To follow the GEM model, I would get students to access the Intro tab of the simulation.  The default is a laser going from air into water; I would explain what the index of refraction is, and then let students play around with it.  While students are exploring the simulation, I would ask generative questions like: “What do you notice about the relationship as you move the light?  What effect does the index of refraction have on the light beam?  Propose an explanation for this.” Once they have had a chance to propose a model, and to test it with various different conditions and extremes, I would have them switch to wave mode and try to propose what is actually happening at the interface to cause this effect.

The next stage is evaluation- having students determine if their model works for various conditions, and to challenge it with scenarios that don’t fit.  Having the students reverse the situation to have light start from water and go into air will cause a cognitive dissonance when the light reflects instead of refracting at the critical angle.  This would cause them to have to rethink and re-evaluate their hypothesis, forcing the third stage of GEM – modification.  This simulation also allows further extension with the use of prisms of various shapes that can demonstrate total internal reflection for example, and extra tools to measure the specific angles, and even the speed of light through the various substances.

These provide many further opportunities for students to go through more GEM cycles as they continue to shape and build their understandings.  This methodology will support what the teacher said in Khan (2007), “I want them to learn chemistry, [but] I don’t want them to just understand the concepts—I want them to understand where to get the concepts and where they come from.”  Later he further explained the premise of the GEM model: “[teachers] lead them through the use of computer simulations in a fashion that lets them look at individual pieces of relationships at a time, and then lead them through putting [those pieces of relationships] together into an overall concept” (Khan, 2010).  Students reported rich benefits, including that “simulations helped them to critically analyze a problem, make unobservable processes more explicit, and contribute to their science learning in ways that go beyond textbooks”, (Khan, 2010).

Digital simulations like PhET can effectively help to support learning.  Khan, (2010), in her conclusion writes “digital technologies such as computer simulations can be particularly engaging for science students because they can manipulate variables in multiple ways and observe changes as a result of this interaction and make predictions”.  Further, simulations may “engage students in multiple GEM cycles in one classroom period, beyond what could be accomplished in the scientific laboratory”, (Khan, 2010).  Khan (2007) stated that “Students expressed enriched mental models of molecular structures when engaged in GEM activities”, that “GEM cycles promoted students’ engagement with generating, evaluating, and modifying hypotheses” and further that “both modeling and inquiry facilitate the development and revision of abstract concepts” all of which serve to emphasize that our students’ understandings can be well supported through a technology integrated GEM model.

• Favale, F., & Bondani, M. (2014). Misconceptions about optics: An effect of misleading explanations? Paper presented at the , 9289 92891A-92891A-5. 10.1117/12.2070520

• Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.
• Khan, S. (2010). New pedagogies for teaching with computer simulations. Journal of Science Education and Technology, 20(3), 215-232.