Many of us who teach physics are enamored by how beautiful the logic of our discipline is. A few simple principles can be logically extended to explain so much of the world. This trait is as true of the subject of color perception as it is to any other subject treated here at The Physics Classroom. Comprehension of the principles of color addition and color subtraction are sufficient for logically reasoning your way through about any question. That is the goal of the Color Addition and Subtraction Concept Builder: to provide students comfort using color addition and color subtraction in order to reason their way through the analysis of a variety of situations. We believe that this Concept Builder represents a great starting point on a journey through the topic of the physics of color.
This Concept Builder utilizes the Incident-Absorbed-Reflected model of describing how we view color. The emphasis of the activity is helping students understand these three important components of color perception - the incident colors of light, the absorbed colors of light, and the refelected colors of light. For simplicity, the model perceives of all colors of light being composed of red, green and blue light. And for further simplicity, the model presented here restricts the discussion to the three primary light colors, the three secondary light colors, white and black. Many teachers will like to take the discussion further (and should) but establishing some clear rules regarding color addition and subtraction is easiest when the discussion is restricted to these eight
colors.
The Color Addition and Subtraction Concept Builder consists of 40 questions organized into 15 Question Groups and spread across three ddifferent activities. The three activities each target a different skill related to color addition and color subtraction. The three activities are described as follows:
- In the Spotlight: Question Groups 1-3 ... To predict the result of adding two primary colors of light.
- Taking Away: Question Groups 4-9 ... To determine what color(s) is/are absorbed if given the incident light colors and the color appearance.
- Do the Math: Question Groups 10-15 ... Identify the color equation for a situation involving color addition and subtraction.
Each activity is quite different. While they can be done independently of each other, we think they are scaffolded in a manner such that one builds upon the other. As such, we recommend starting with the first activity and working through them in order. Teachers are encouraged to view the
questions in order to judge which activities are most appropriate for their classes.
In order to complete an activity, a student must correctly analyze each question in that activity. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the activity. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through an activity, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question in an activity has been analyzed, the student earns a trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned activities.
The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise.