THE STUDY OF LIGHT

Unlike mathematics, in which topics such as whole-number arithmetic are foundational for the study of rational number, and both are foundational for the study of functions, there is currently little agreement on the selection and sequencing of specific topics in science, particularly at the elementary level.3 What clearly is foundational for later science study, however, is learning what it means to engage in scientific inquiry—learning the difference between casual and scientific investigations. That learning can be accomplished in the context of many different specific topics.

In this chapter, we choose light as our topic of focus because it affords several benefits. The first is practical: the topic involves relatively simple concepts that children can understand from investigating with relatively simple materials. For example, our bodies and the sun make shadows that can be studied, and similar studies can occur with common flashlights and classroom materials. Pencil and paper, and perhaps some means of measuring distance, are all that is needed for data collection. Children can also study light using simple light boxes (Elementary Science Study’s Optics unit4) in which light bulbs are placed in cardboard boxes containing openings covered with construction paper masks that control the amount of light emanating from the box. Thin slits in the masks make the thin beams of light necessary for studies of reflection and refraction. Multiple wider openings covered with different colored cellophane filters enable investigations mixing colors of light. And again, pencil and paper are all that are needed for data collection showing the paths of light.

In addition, developing scientific knowledge of light challenges us to conceptualize aspects of the world that we do not directly experience—a critical element of much scientific study. For example, light travels, yet we do not see it do so; we infer its travel when we turn on a flashlight in the dark and see a lighted spot across the room.

Developing scientific knowledge often requires conceptual change5 in which we come to view the physical world in new ways.6 Students must learn that things are not always what they seem—itself a major conceptual leap. The study of light gives children an accessible opportunity to see the world differently and to challenge their existing conceptions. We see the world around us because light reflects from objects to our eyes, and yet we do not sense that what we see is the result of reflected light.

Some children, moreover, view shadows as objects instead of understanding that shadows are created when light is blocked. Conceptual development is required if they are to understand the relationship among a light source, an object, and the shadow cast by that object. Working with flashlights can provide children an opportunity to challenge directly everyday conceptions about shadows, providing them with a powerful early experi-



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