### Notes:

The Color Addition and Subtraction Concept Builder is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Concept Builder can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

### Teaching Ideas and Suggestions:

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.

### Related Resources

There are a numerous resources at The Physics Classroom website that serve as very complementary supports for the Color Addition and Subtration Concept Builder. These include:

Most students will find that  Lesson 2 of the Light Waves and Color Chapter of the Tutorial is a perfect accompaniment to this Concept Builder. In particular, the following three pages will be most helpful:

Light Absorption, Reflection, and Transmission

Color Subtraction

• Curriculum Corner
The Curriculum Corner section of our website contains a complete course curriculum that coordinates with our Tutorial section and our Minds On Physics program. There are a few activities in the Light and Color section that would be useful complements to this activity. These include:

Reflection, Transmission and Color

Viewed in Another Light

Visit Light and Color section of the Curriculum Corner.

• Minds On Physics Internet Modules:
The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignments LC3, LC4, LC5, and LC6 of the Light and Color module are great complements to this Concept Builder. They are best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.

Users may find that the App version of Minds On Physics works best on their devices. The App Version can be found at the Minds On Physics the App section of our website. The Light and Color module can be found on Part 5 of the six-part App series. Visit Minds On Physics the App.

• Physics Interactives:
The Physics Interactives section of our website includes a collection of interactive simulations that allow learners to explore variable relationships, identify patterns, and investigate physical concepts that underlie the physical world. Two of the Interactives in our Light and Color section makes a perfect complement to this Concept Builder. The provides students with an interactive light box for mixing light colors with a variable intensity. Combined with lab activities, it is a great starting point into the topic of color. The Stage Lighting Interactive allows a student to explore how the pigments in an actors clothing interact with the incident light to affect the color appearance of the clothing under various stage lights.