One of the most fundamental laws in ray optics is the law of reflection. While it is a simple law to comprehend, understanding is critical to the construction of ray diagrams and an understanding of other phenomenon such as specular vs. diffuse reflection, total internal reflection, and image formation by plane mirrors.

In this Law of Reflection Concept Builder, students get plenty of practice comprehending the law of reflection for plane mirrors. All questions involve the same task - identifying the appropriate reflected ray from among 8 options. Tapping on the diagram will toggle through those 8 options one-by-one. Once the appropriately-directed reflected ray is displayed, students can tap on the Check Answer button and get immediate feedback.

This Concept Builder was intended as an in-class activity. After some early lab investigation, some discussion and demonstrations of the law of reflection, allow students an opportunity to interact with the questions. This Concept Builder consists of three separate difficulty levels. The Apprentice Difficulty Level has only 4 questions. The questions all include a horizontal or a vertical mirror surface. There is a protractor in the background that allows students to make a measurement of the incoming and the outgoing angles. The Master Difficulty Level includes eight questions - the four questions from the Apprentice level plus four additional questions with angled mirrors. The Wizard Difficulty Level also includes eight questions. The eight questions include the four questions from the Master DIfficulty Level with the angled mirrors plus four additional angled-mirror questions. For teachers who wish to reduce the time spent on the activity, we recommend doing the Apprentice Difficulty Level (as a warm-up) followed by the Wizard Difficulty Level.

In order to complete a level, a student must correctly analyze each question of that level. 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 level. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through a level, 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 of a difficulty level 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 levels.

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 few resources at The Physics Classroom website that serve as very complementary supports for The Law of Reflection Concept Builder. These include:
 

• Reading:
  Most students will find that  Lesson 1 of the Reflection and the Ray Model of Light Chapter of the Tutorial is a perfect accompaniment to this Concept Builder. In particular, the following two pages will be most helpful:
  
  The Law of Reflection
  
  Specular vs. Diffuse Reflection
  
  
   
• 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 Reflection and Mirrors section that would be useful complements to this activity. These include:
  
  Light Reflection
  
  Specular vs. Diffuse Reflection
  
  Visit Reflection and Mirrors 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. Assignment RM1 of the Reflection and Mirrors module is a great complement to this Concept Builder. It is 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 Reflection and Mirrors module can be found on Part 6 of the six-part App series. Visit Minds On Physics the App.
  
  
   
• The Laboratory:
  There is no substitute for hands-on activities. And at The Physics Classroom, those hands-on activities can be found in The Laboratory section of the website. The following lab makes a useful pre-cursor to this Concept Builder.
  
  Reflection Lab
  
  Visit The Laboratory
  
   

Additional resources and ideas for incorporating this Law of Reflection Concept Builder into an instructional unit on Reflection and Mirrors can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.