### Notes:

The Wave Interference 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:

Most teachers who teach a unit on waves or on waves and sound will spend a portion of time discussing wave behaviors like interference. An understanding of interference is necessary for understanding other concepts such as standing wave formation and standing wave patterns, sound resonance, harmonics, and beats. This Concept Builder focuses on the concept of interference and upon how interference results in a pattern that is the combined result of the two interfering waves. There are three activities in this Concept Builder, each with a different emphasis. The three activities can be described as follows:

• To Construct or To Destruct: Question Groups 1-4. Learners are presented with two interfering waves. They must identify the type of interference at five different locations as being examples of constructive or destructive interference. There are two questions in each Question Group. Questions are selected at random and so the order in which questions are delivered to the students varies. If a student misses one of the questions in a Question Group, they will have to get the second question correct. Once they do, they will be given the first question again. Once they have answered both questions correctly, they receive a star for that Question Group and it is removed from the cue of questions that they must answer.
• The Principle of Superposition: Question Groups 5-8. Learners are presented with two interfering waves and a background grid. They must use the principle of superposition to determine the displacement of the medium at three specified locations. Like the first activity, there are two questions in each of the four Question Groups. The order of presentation of questions is scrambled on a per student basis. There are three answers for every question. If a student misses one or more of the three questions, they will be given a second chance before their answers are considered incorrect. A green check will cover the correct answer(s) and they will have one last opportunity to correct their wrong answers. Like the first activity, if a student misses one of the questions in a Question Group, they will have to get the second question correct. Once they do, they will be given the first question again. Once they have answered both questions correctly, they receive a star for that Question Group and it is removed from the cue of questions that they must answer.
• Sum It Up: Question Groups 9-10. Learners are presented with two interfering waves and a background grid. There are nine specified locations along the medium for which learners must identify the location of the medium at each location that would result from the interference of the two given waves. There are dots for each location. They must drag each do to the proper height above or below the rest position to indicate where the medium would be displaced to at that location. If they are correct (with a small margin of error), then the dot snaps into its proper place. If they are incorrect, the do returns to its starting position and they have to try again. Once all dots have been properly placed, the resultant wave is drawn and the question is considered correct. There are two Question Groups - one is characterized by constructive interference at all nine locations and the other involves destructive interference.

To gain a feel for the cognitive difficulty of this Concept Builder, we recommend that teachers attempt to complete one of the difficulty levels. Alternatively, the questions are provided in a separate file for preview purposes. In order to complete an activity, a student must correctly analyze each question for 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 activity. 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 numerous resources at The Physics Classroom website that serve as very complementary supports for the Wave Interference Concept Builder. These include:

• 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 WM6 of the Waves Motion module provides 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 Static Electricity module can be found on Part 5 of the six-part App series. Visit Minds On Physics the App.

• Physics Interactives: Waves and Sound Section
Our Physics Interactives section offers a collection of interactive simulations. Each simulation offers students a variable-rich environment that allows them to explore a concept or phenomenon. Our Wave Addition Interactive is a perfect accompaniment to this Concept Builder.

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