This unit builds toward these performance expectations:

• HS-PS2-5* Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.
• HS-PS4-1 Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media.
• HS-PS4-2 Evaluate questions about the advantages of using digital transmission and storage of information.
• HS-PS4-3 Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other.
• HS-PS4-4 Evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.
• 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.
• HS-ESS2-4† Use a model to describe how variations in the flow of energy into and out of Earth’s systems result in changes in climate.

PS2.B: Types of Interactions

• Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnetics or electric currents can cause magnetic fields; electric charges or changing magnetic fields can cause electric fields. (HS-PS2-5)

PS3.A: Definitions of Energy

• These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as either motions of particles or energy stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space. (HS-PS3-2)

PS4.A: Wave Properties

• The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the types of wave and the medium through which it is passing. (HS-PS4-1)
• Waves can add or cancel on another as they cross, depending on their relative phase (i.e., relative position of peaks and troughs of the waves), but they emerge unaffected by each other. (HS-PS4-3)
• Information can be digitized (e.g., a picture stored as the values of an array of pixels); in this form, it can be stored reliably in computer memory and sent over long distances as a series of wave pulses. (HS-PS4-2, HS-PS4-5)

PS4.B: Electromagnetic Radiation

• Electromagnetic radiation (e.g., radio, microwaves, light) can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features. (HS-PS4-3)
• When light or longer wavelength electromagnetic radiation is absorbed in matter, it is generally converted into thermal energy (heat). Shorter wavelength electromagnetic radiation (ultraviolet, x-rays, gamma rays) can ionize atoms and cause damage to living cells. (HS-PS4-4)
• Photovoltaic materials emit electrons when they absorb light of a high-enough frequency. (HS-PS4-5)

PS4.C: Information Technologies and Instrumentation

• Multiple technologies based on the understanding of waves and their interactions with matter are part of everyday experiences in the modern world (e.g., medical imaging, communications, scanners) and in scientific research. They are essential tools for producing, transmitting, and capturing signals and for storing and interpreting the information contained in them. (HS-PS4-5)

ESS2.D Weather and Climate

• The foundation for Earth’s global climate systems is the electromagnetic radiation from the sun, as well as its reflection, absorption, storage, and redistribution among the atmosphere, ocean, and land systems, and this energy’s re-radiation into space.

This unit intentionally develops students’ engagement in these practice elements:

Developing and using models in 9–12 builds on K–8 experiences and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. The following elements of this practice are intentionally developed across this unit:

• Develop, revise, and/or use a model based on evidence to illustrate and/or predict the relationships between systems or between components of a system.
• Develop and/or use multiple types of models to provide mechanistic accounts and/or predict phenomena, and move flexibly between model types based on merits and limitations.

Planning and carrying out investigations in 9–12 builds on K–8 experiences and progresses to include investigations that provide evidence for, and tests of, conceptual, mathematical, physical, and empirical models. The following elements of this practice are intentionally developed across this unit:

• Plan an investigation or test a design individually and collaboratively to produce data to serve as the basis for evidence as part of building and revising models, supporting explanations for phenomena, or testing solutions to problems. Consider possible confounding variables or effects and evaluate the investigation’s design to ensure variables are controlled.
• Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.
• Plan and conduct an investigation or test a design solution in a safe and ethical manner including considerations of environmental, social, and personal impacts.

Obtaining, evaluating, and communicating information in 9–12 builds on K–8 experiences and progresses to evaluating the validity and reliability of the claims, methods, and designs. The following elements of this practice are intentionally developed across this unit:

• Critically read scientific literature adapted for classroom use to determine the central ideas or conclusions and/or to obtain scientific and/or technical information to summarize complex evidence, concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms.
• Compare, integrate and evaluate sources of information presented in different media or formats (e.g., visually, quantitatively) as well as in words in order to address a scientific question or solve a problem.
• Gather, read, and evaluate scientific and/or technical information from multiple authoritative sources, assessing the evidence and usefulness of each source.
• Evaluate the validity and reliability of and/or synthesize multiple claims, methods, and/or designs that appear in scientific and technical texts or media reports, verifying the data when possible.

Elements from the following practices are also key to the sensemaking in this unit:

• Asking Questions and Defining Problems
• Analyzing and Interpreting Data
• Using Mathematics and Computational Thinking
• Building Explanations and Designing Solutions
• Engaging in Argument from Evidence

This unit intentionally develops students’ engagement in these crosscutting concept elements:

Cause and effect: Mechanism and explanation. Events have causes, sometimes simple, sometimes multifaceted. A major activity of science is investigating and explaining causal

relationships and the mechanisms by which they are mediated. The following elements of this crosscutting concept are intentionally developed across this unit:

• Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.
• Classifications or explanations used at one scale may fail or require revision when information from smaller or larger scales is introduced, thus requiring improved investigations and experiments.

Energy and matter: Flows, cycles, and conservation. Tracking fluxes of energy and matter into, out of, and within systems helps students understand the systems’ possibilities and limitations. The following elements of this crosscutting concept are intentionally developed across this unit:

• The total amount of energy and matter in closed systems is conserved.
• Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system.
• Energy cannot be created or destroyed—it only moves between one place and another place, between objects and/or fields, or between systems.

Structure and function. The way in which an object or living thing is shaped, and its substructure, determine many of its properties and functions. The following elements of this crosscutting concept are intentionally developed across this unit:

• Investigating or designing new systems or structures requires a detailed examination of the properties of different materials, the structures of different components, and connections of components to reveal its function and/or solve a problem.
• The functions and properties of natural and designed objects and systems can be inferred from their overall structure, the way their components are shaped and used, and the molecular substructures of its various materials.

Elements from the following crosscutting concepts are also key to the sensemaking in this unit:

• • Patterns
  • Systems and Systems Models

Which elements of the Nature of Science (NOS) are developed in the unit?

• Scientific Investigations Use a Variety of Methods. Scientific investigations use a variety of methods, tools, and techniques to revise and produce new knowledge.
• Scientific Knowledge Is Based on Empirical Evidence. Science disciplines share common rules of evidence used to evaluate explanations about natural systems.
• Scientific Knowledge Is Open to Revision in Light of New Evidence. Most scientific knowledge is quite durable but is, in principle, subject to change based on new evidence and/or reinterpretation of existing evidence.

How are they developed?

• In Lesson 3, the teacher reminds students that their work throughout this lesson using physical models and simulations is a reflection of the nature of science: physical models allow scientists to directly observe changes in a system that results from manipulating variables of interest, such as the amplitude and frequency, and simulations enable them to study complex phenomena, such as particle behavior on a string, to further their understanding.
• In Lessons 8 and 13, the teacher reminds students that their work throughout this unit has been a reflection of the nature of science: Scientists work to answer questions they have about natural phenomena, such as the way microwave ovens work. These questions motivate the need to use different methods, such as investigations, simulations, or discussions to gather and evaluate data that could help them make sense of various phenomena. In this unit, student questions motivate a set of explorations to build and refine models that could better explain their questions about how EM waves work.
• In Lesson 8, after students develop a model of energy transfer inside the microwave oven, the teacher reminds students that one way to test the power of their model is to use it to make predictions about energy transfer in the microwave oven when matter is heated using the turntable.
• In Lesson 10, when students identify the limitations of the wave model of light to explain their observations, the teacher mentions that historically, scientists believed that light was purely a wave phenomenon, but that similarly to our experience, this model did not match their observations, which led them to revise their ideas about the behavior of light.

Which elements of ETS are developed in the unit?

• Influence of Science, Engineering, and Technology on Society and the Natural World. Engineers continuously modify these technological systems by applying scientific knowledge and engineering design practices to increase benefits while decreasing costs and risks.

How are they developed?

• In Lesson 11, students read about digital and conventional radiography and learn about how technological advances have enabled ionizing radiation use while decreasing costs and risks.

This unit is anchored by a short news article explaining that some people are using their microwave ovens to store electronics. This is followed by a series of in-class demonstrations using a microwave oven, including playing music on a Bluetooth speaker from a device inside the oven and heating a plate of nachos (or a similar food). Students draw on their personal experiences of heating food to make predictions about how to transfer energy quickly into matter. The use of a microwave oven both to block wireless signals and to heat food provides the context in which to investigate the nature of energy transfer through waves, properties of waves, the interactions of electromagnetic (EM) radiation with various particles, the use of EM radiation in our daily lives, and safety considerations when using those technologies.

The microwave oven anchoring phenomenon was chosen from a group of phenomena aligned with the target performance expectations based on the results of two focus groups with high schoolers from across the country, and in consultation with external advisory panels that included teachers, subject matter experts, and state science administrators. This unit was adapted from a previous unit, and therefore did not follow the same selection process as other OpenSciEd HS units. The microwave oven anchor was chosen for the following reasons:

• Teachers and administrators saw high relevance to students’ everyday experiences.
• Students found the phenomenon compelling and had dozens of relevant questions.
• Explaining how the microwave oven heats food addresses all the DCIs in the bundle at a high school level.
• Students have a unique opportunity to generate observable EM radiation in the classroom with a microwave oven and use it to investigate the interactions between EM radiation and matter.
• The microwave oven shares components with many other forms of technology that are relevant to students’ lives.

This unit is the fifth in the OpenSciEd High School Physics course sequence. It is designed to build on student ideas about energy transfer and forces from previous units, and apply these ideas in the context of waves and electromagnetic radiation. In the first unit of the course, OpenSciEd Unit P.1: How can we design more reliable systems to meet our communities’ energy needs? (Electricity Unit), students develop ideas around energy transfer and conservation in the context of charged particles (electrons) colliding with other electrons (electricity) to transfer energy across great distances. In the second unit of the Physics course, OpenSciEd Unit P.2: How forces in Earth’s interior determine what will happen to its surface? (Earth’s Interior Unit), a sudden rip in Earth’s crust motivates the need to consider forces to explain our observations. In the third unit, OpenSciEd Unit P.3: What can we do to make driving safer for everyone? (Vehicle Collisions Unit), students develop a more robust understanding of forces as vectors and use conservation of momentum to make predictions about the outcomes of collisions. In the fourth unit, OpenSciEd Unit P.4: Meteors, Orbits, and Gravity (Meteors Unit), students expand their model of forces to include the force of gravity at great distances, using ideas about fields developed in the first unit to understand the relationships between gravity and energy transfer. In this unit, OpenSciEd Unit P.5: How do we use radiation in our lives and is it safe for humans? (Microwave Unit), students use energy transfer, electromagnetism, wave mechanics, and forces at a distance to explain how food heats up in a microwave and how this technology might be dangerous for humans (and also save lives). In the final unit, OpenSciEd Unit P.6: Earth’s History and the Big Bang (Cosmology Unit), students will explore cosmology and the Big Bang, applying ideas about forces and energy from all five previous units on the largest scale.

The unit is organized into two main lesson sets. Lesson Set 1 (Lessons 1-8) focuses on developing science ideas about energy transfer through waves and changing electric and magnetic fields. These lessons also cover how the structure of the microwave oven and the type of substance within the oven influences how well a material absorbs wave energy. Lesson Set 2 (Lessons 9-13) shifts the focus to examining other types of EM radiation, their uses, interactions with various materials, and safety considerations based on what is learned in Lesson Set 1 about wave and particle interactions. Students apply these ideas in a transfer task in Lesson 13.

In the first lesson set (Lessons 1-8), students notice patterns when heating food in a microwave oven, and develop models for how the structure of a microwave oven affects energy transfer to the food inside of it and how it can affect wireless signals. They watch a dissection of a microwave oven and learn that this device is designed so the magnetron antenna changes electric fields near the oven’s cooking area. They investigate wave properties using a string in a simulation, as well as waves on a physical spring, to determine how waves can transfer energy. This leads them to wonder about the nature of the waves in a microwave oven and what could be producing them. They investigate how moving electrons in an antenna can cause changing electric fields that travel through space, and measure the magnetic field around a current-carrying wire to understand the relationship between electric and magnetic fields. They then design an investigation to determine what happens to the microwave radiation when it reaches the material(s) in the door and walls, and find evidence suggesting that energy transferred by microwave radiation can be absorbed, reflected, and/or transmitted by matter. For the mid-unit assessment, students use the science ideas they have developed about the interactions of different types of EM radiation with different types of matter to explain how an increase in greenhouse gases could be contributing to the overall increase in global temperatures.

In the last two lessons of the first lesson set, students will use simulations to investigate how particles of different materials (water, plastic, metal) interact with changing electric fields, and connect this particle-scale evidence to macroscopic evidence about materials heating up in the microwave oven. They will use these ideas to consider the validity and reliability of claims about the safety of using metal in the microwave oven. Finally, they use simulations to make sense of wave interference to explain the hot and cold spots produced by the microwave oven. By the end of this lesson set, students are ready to explain how a microwave oven uses the principles of wave behavior to transfer energy into food, but they still have questions about the safety of this technology, and how other forms of radiation are used. This lesson set builds toward the DCI elements associated with the following performance expectations: HS-PS2-5*, HS-PS4-1, HS-PS4-5, and HS-ESS2-4†.

In the second lesson set (Lessons 9-13), students build out the electromagnetic spectrum after organizing different forms of radiation in a card sort, and argue about how the properties of EM radiation and its interactions with matter can help explain its uses. They use multiple sources of evidence to try to identify patterns in frequency, amplitude, and skin cancer, and read about the dual nature of EM radiation as a way to explain ionizing radiation. Students wonder about other uses of EM radiation, and read about digital and conventional radiography to explain the advantages and disadvantages of storing information digitally. Students develop a system to send messages with EM waves using a simulation, and use these ideas together with information from multiple sources to explain how wireless electronic devices are designed to use EM waves to reliably communicate different types of information, adding to their understanding of wave behavior associated with HS-PS4-5. In the transfer task, students use their understanding of EM radiation and its associated technologies to evaluate two social media posts about 5G radiation, and use the model for EM radiation to argue from evidence about whether this technology is safe. The lesson set builds toward the DCI elements associated with the following performance expectations: HS-PS4-2, HS-PS4-3, and HS-PS4-4.

This is the fifth unit of the High School Physics Course in the OpenSciEd Scope and Sequence. Given this placement, several modifications would need to be made if teaching Physics first, or teaching this unit earlier in the Physics course. These include the following adjustments:

• If taught before OpenSciEd High School Chemistry, supplemental teaching of the particle model of matter will be required, including conceptual understanding of the nature of electrons, nuclei, atoms, molecules, and polarity. You will also need to review the nature of thermal energy and thermal energy transfer.
• If taught earlier in the school year, supplemental teaching of the relationship between energy and forces, the nature of forces at a distance, basic properties of mechanical waves, and the fundamentals of electricity will be required.
• If taught as part of an AP Physics course, be prepared to provide students with additional support around equations that are not treated in depth.

The following are example options to shorten or condense parts of the unit without eliminating important sensemaking:

• Lesson 5: Instead of providing time for small groups to design their investigations at the end of day 2, you can have the class develop an investigation plan together. This approach will limit students’ individual engagement in planning and carrying out investigations, but it will save you time as groups won’t need to argue for their plans in front of the class and reach a consensus on which investigations to focus on.
• Lessons 6 features the first transfer task of the unit, which includes an ESS Performance Expectation. If this is not a priority for your school or district, you can skip this assessment. We suggest you design an alternative assessment with an equally complex phenomenon, as this is an ideal moment in the unit to assess students’ understanding about absorption, reflection, and transmission of EM radiation.

To extend or enhance the unit, consider the following:

• Lesson 2: Cavity magnetrons are very complicated, and the science ideas needed to explain in detail how they work are far beyond what is expected of high school students. However, some students may be eager to explore circuits and magnetrons or be more engaged by university-level physics topics. As an extension activity, you can ask them to research capacitors and inductors (they can search for information about LC oscillations), or allow them to safely experiment with capacitors and inductors on a breadboard connected to an oscilloscope to produce LC oscillations. They will gain a much more nuanced understanding of the magnetron, as well as the ability to make connections back to the circuitry they worked with in Electricity Unit.
• Lesson 3: Give students extra time to test the mathematical model. See teacher guide for additional information.
• Lesson 5: Give students additional materials and time to carry out their own  investigations. This will require additional time assessing the safety of each of the investigations students will carry out, but it will give students the opportunity to gather data they considered as appropriate to answer their own questions. You may also want to consider taking an extra period for classes in which there is student engagement around the need for additional tests beyond the three defaults outlined in the lesson.
• Lesson 6: Spend more time on evaluating the interactions of EM radiation with greenhouse gases. You could accomplish this by discussing the ways students answered the questions to the transfer task.
• Lesson 7: Investigate how different food types (proteins, carbohydrates, fats) interact with microwave radiation, drawing connections between the polarity of the molecules and their ability to absorb energy.
• Lessons 7 and 12: Provide students with the opportunity to obtain information on the internet about claims regarding the safety of microwave radiation (Lesson 7) and the safety of wireless communication (Lesson 12), and evaluate their validity and reliability.
• All lessons: Remove scaffolds provided with Science and Engineering Practices (SEPs) as a way to give students more independent work with the elements of these practices.

• Diego Rojas-Perilla, Revision Unit Lead, BSCS Science Learning
• Nicole Vick, Field Test Unit Lead, Northwestern University
• Zoë Buck Bracey, Writer, BSCS Science Learning
• Joe Kremer, Writer, Denver Public Schools
• Whitney Mills, Writer, BSCS Science Learning
• Michael Novak, Writer, Northwestern University
• Laura Zeller, Writer, BSCS Science Learning
• Kate Berger, Teacher Advisor, Denver Public Schools
• Luis De Avila, Teacher Advisor, Denver Public Schools
• Kathryn Fleegal, Teacher Advisor, Denver Public Schools
• Justin Jeannot, Teacher Advisor, Denver Public Schools
• Ken Roy, Safety Consultant, National Safety Consultants, LLC

• Madison Hammer, Production Manager, University of Colorado Boulder
• Kate Herman, Copy Editor, Independent Consultant 
• Erin Howe, Project Manager, University of Colorado Boulder
• Tyler Morris-Rains, BSCS Science Learning
• Jamie Deutch Noll, BSCS Science Learning

An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has earned the highest score available and has been awarded the NGSS Design Badge. You can find additional information and read this unit’s review on the nextgenscience.org website.