Basking in reflected light

Meera Chandrasekhar and Dorina Kosztin

Light and how it behaves, has fascinated and puzzled humans since time immemorial. Much of what humans observe about light comes from how light interacts with the various materials within our view.

Young students’ conceptions about light can confound adults who have learned about the physics involved in how light behaves. Yet it is important for the teacher to know where students will trip up, so we can set up our teaching and discussions so that misconceptions are revealed, confronted, and dispelled.

Basking-Refl-Light In this article we will present a series of activities for use in the classroom. We begin with an activity to introduce students to how different kinds of materials and their surfaces modify the behaviour of the light that falls on them. This activity is followed by a reading page and an exploratory activity in which students examine the reflection of light. A quantitative activity, in which students discover the laws of reflection, is followed by an activity in which students apply what they have learned about light in building a periscope. These activities were used as part of an extra-curricular program called Exploring Physics, a program for students in grades 4-6 in Columbia, Missouri, USA.

All the activities that we will present are best performed in groups of two or three students. Students are given the materials, and are expected to make observations and discuss them among the group. They write their observations and interpretations of observed phenomena in their individual notebooks. It is all right if their initial statements are not completely accurate. Responses may be based on students’ misconceptions, and should be used by the teacher to guide later discussions to dispel misconceptions. As the activity progresses, the teacher asks student groups to share their observations so that the entire class can be involved in the discussion. The teacher should ensure that all groups provide inputs. One method of doing so is to call on each group to provide inputs on one aspect. If you have small dry-erase boards (whiteboards) or small chalkboards in the classroom, student groups can write or draw their inputs on their board, which they hold up while reporting back. The teacher guides the discussion with questioning so that students can reason through their deductions and justify their answers, or correct the answer if necessary.

Meera Chandrasekhar is a Professor of Physics at the University of Missouri in Columbia, Missouri. Dorina Kosztin is a Teaching Professor at the University of Missouri in Columbia, Missouri. They can be reached at meerac@missouri.edu and kosztind@missouri.edu.

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