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 If This ... Then That 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.

Every question in this Concept Builder has the same format. Two diagrams showing the incident light upon a shirt and the appearance of the shirt are provided. Using an understanding of color addition and color subtraction, students must determine how the shirt interacts with each of the three primary colors of light. Then a third diagram with a third incident light color is given and students must determine the color appearance of the shirt. This format forces students to think systematically about which primary color(s) is/are being absorbed and which primary color(s) is/are being reflected.

We suggest that students use the Incident-Absorbed-Reflected model when approaching these questions. If you are unfamiliar with the model, you can learn about it if you visit any of the Help pages that accompany each question in the Concept Builder. An index page that links to each of the 12 Help pages can be accessed here.

The If This ... Then That: Color Concept Builder consists of 27 questions organized into 12 Question Groups and spread across three difficulty levels. The three difficulty levels differ in terms of the number of questions and the complexity of the color combinations that are given. The three difficulty levels are differentiated as follows:
 

• Apprentice Difficulty Level: Question Groups 1-4 ... Includes the least complex color combinations.
• Master Difficulty Level: Question Groups 1-8 ... Color combinations vary from the easiest to moderate difficulty.
• Wizard Difficulty Level: Question Groups 5-12 ... Includes the most complex color combinations.

As you can see there is some redundancy in the levels The Master level includes Question Groups from the Apprentice level and the Wizard level includes some Question Groups from the Master difficulty level. As such, teachers are encouraged to view the questions in order to judge which difficulty levels 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.
 

There are a numerous resources at The Physics Classroom website that serve as very complementary supports for the If This ... Then That: Color Concept Builder. These include:
 

• Reading:
  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 Addition
  
  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
  
  Color Addition and Subtraction
  
  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 LC4, LC5, LC6, and LC7 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.
  
   

Additional resources and ideas for incorporating the If This ... Then That: Color Concept Builder into an instructional unit on Light and Color can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.