##
* *Reflection: Checks for Understanding
Standing Waves - Section 2: Standing Wave Simulation

As much as possible, I like to have students develop their own understanding through observation. For instance, in this assignment, I tell the students the location of nodes and anti-nodes on the simulator and have them define these words based on what they see. Student Work - Standing Waves Front shows two examples of typical student responses; one says that a "node is a point along the medium that appears to stand still", the other says it is "where the wave is on the equilibrium" (preview mode only shows the first page, download this PDF to see the complete document). These are fine definitions that are the same as a textbook definition of node as "points of no displacement". When students construct their own understanding, the material if more meaningful to them and they find it easier to apply to more advanced ideas such as standing wave formation in an instrument.

The Student Work - Standing Waves Back shows samples of the explanation provided by the Physics Classroom (preview mode only shows the first page, download this PDF to see the complete document). I have students write this on the sheet so that they can compare it to their own explanation and see how the two explanations differ. Specifically, they explain what information they think they missed in their original definition on the front. It is good to see that students are able to pull that information out of the reading and communicate it on the handout.

Finally, the assignment finishes with applications of how standing waves form on a guitar string. Again, it is essential to link this theoretical knowledge to some real-life examples and the students are able to do that.

*Checks for Understanding: Standing Waves Activity - Student Work*

# Standing Waves

Lesson 3 of 15

## Objective: Students construct an explanation for how standing waves form using wave vocabulary words.

Due to standardized state testing, we have a half-day today so the class period is only 30 minutes long. In the previous class, Slinky Rules, students learn about interference and wave reflection. Now they apply that understanding to explain how standing waves form. They use a simulation to explore the creation of a standing wave and then use wave vocabulary to construct an explanation. Computers for students and a standing wave demonstrator are needed for this lesson.

To complete this lesson, students apply CCSS Math Practice 5: Use appropriate tools strategically and Math Practice 7: Look for and make use of structure. As they develop an explanation for how standing waves form, they apply NGSS Science Practice 2: Developing and using models and Science Practice 6: Constructing explanations. The NGSS Performance standards applied are HS-PS4-1: Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media and HS-PS4-5: Communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy.

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#### Standing Wave Simulation

*25 min*

Students learn that waves interfere constructively and destructively in Slinky Rules. Now they learn how about standing waves. I tell the students that without standing waves, music and musical instruments would not exist. A sustained musical note is not possible without the formation of a standing wave. Today they explore the concept of standing waves and construct an explanation of how they form.

The standard seating for my students is groups of 4 students at two tables pushed together. Since time is short today, I have students work with one of the partners at their desk. Each partnership gets a computer and a copy of the Standing Wave Activity which students fill out in pairs. The handout has students navigate to Walter Fendt's webpage of physics Java programs (http://www.walter-fendt.de/ph14e), scroll down to the "Oscillations and Waves" section and open Standing Wave (Explanation by Superposition with the Reflected Wave) Java program. This program shows an incoming periodic wave that reflects off of a barrier, which I discuss in Standing Wave Java Demo. As this happens, students see a standing wave form with nodes and anti-nodes. They construct an explanation of how a standing wave forms using wave vocabulary words such as constructive interference, destructive interference, incident, and reflected waves.

After this, students navigate to The Physics Classroom page on Standing Wave Formation and use the information there to check if their explanation of how a standing wave forms matches what is on the Physics Classroom page. While students work on the activity, I invite groups up to observe the standing wave generator I have set up at the front of the room. It is important to expose students to real-life examples as much as possible so that they know what is described in the textbooks is true. At the end of class, I collect student work to check for understanding.

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For homework, students are to complete a Socrative quiz Intro to Waves - Big Ideas; though it is a quiz, this counts as a homework grade. Socrative is a great tool that allows students to answer questions using their smart phones or computers and the program grades the results. The goal of this homework is to reinforce the big ideas of the unit that have been explored so far. Those are:

1. The velocity of a wave is determined by the medium.

2. The frequency of a wave is determined by the wave source.

3. The wavelength is a result of the frequency and velocity according to the wave equation.

4. The amplitude of a wave is determined by the energy of a wave.

5. The amplitudes of separate waves add together when waves interfere.

During the next class period, we review the quiz using Intro to Waves - Big Ideas Solutions.

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- LESSON 1: Wave Hello
- LESSON 2: Slinky Rules
- LESSON 3: Standing Waves
- LESSON 4: Standing Waves Demonstrations
- LESSON 5: Resonance
- LESSON 6: Design Your Own Instrument
- LESSON 7: Overtones in Musical Instruments
- LESSON 8: Observations On The Doppler Effect
- LESSON 9: Doppler Effect Equation
- LESSON 10: Wave Quiz Prep
- LESSON 11: Wave Quiz
- LESSON 12: Mixing Colors with Light
- LESSON 13: Electromagnetic Spectrum Mapping
- LESSON 14: What Materials Block Your Phone's Signal?
- LESSON 15: Speed of Light Vs. Speed of Sound