# Electromagnetic Spectrum Mapping

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## Objective

Students learn the parts of the electromagnetic spectrum and develop an understanding of how it interacts with matter.

#### Big Idea

When electromagnetic waves interact with matter, they are either absorbed, reflected or transmitted.

## Context and Supplies

In the previous lesson, Mixing Colors with Light, students connected different colors of visible light to the frequency of that light. Today, we extend the range of frequencies to the rest of the electromagnetic spectrum. Students make an chart that labels the different parts of the electromagnetic spectrum, including the frequency and wavelength ranges. Students also spend time reading about the electromagnetic spectrum and make connections between frequency, wavelength and energy as well as how light behaves as it interacts with matter.

This lesson involves NGSS Science Practice 2: Developing and using models as the electromagnetic spectrum is represented with a diagram. Students also have to apply Science Practice 4: Analyzing and interpreting data, Science Practice 6: Constructing explanations (for science) and designing solutions (for engineering) and Science Practice 7: Engaging in argument from evidence as they read about how the different parts of the electromagnetic spectrum interact with matter. This is in the context of performance standard 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-PS4-4: Evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.

## How We See Color Review

10 minutes

In the previous lesson, Mixing Colors with Light, students had a homework assignment to watch video on how the human eye perceives color. We spend the first few minutes of today's class reviewing that assignment. With the How We See Color - Solutions in hand, I call on random students to supply an answer for each question. While students supply their answers, I walk around the room to check that students completed the homework assignment. If they did, they receive a grade for effort.

After we complete the 8 questions that were on the "Think" portion of the How We See Colors TED-Ed video site, I have students do a turn and talk to answer the following question: "What surprised you about how we see colors?" Students discuss this question and put their answer on the mini-white board at each desk. After a minute, we go around the room and the groups share out their answer. Students are surprised to learn that we are only able to perceive three different colors (red, green and blue) and that other colors stimulate a combination of the receptors in our eyes to produce the perception of that color. They also find it interesting that we have separate receptors for low light and that there is no color information in that part of our vision. Next we extend this understanding of light frequency and wavelength to the rest of the electromagnetic spectrum.

## Students Make Electromagnetic Spectrum Chart

30 minutes

Students learn that different colors of light are just different frequencies of light. Now students move beyond visible light into to the different regions of the electromagnetic spectrum. I display the Make Spectrum Chart power point which instructs students create a hand-drawn picture of the entire electromagnetic spectrum, labeling each region. Their diagram needs to include the frequency ranges and wavelengths for each region and a description of one technology for each region. I give students 25 minutes to complete their charts; I ask each student to make his or her own.

To complete this assignment, students are free to use resources in the classroom such as physics textbooks and computers that have internet access. There is no shortage of electromagnetic spectrum charts available, so students have a lot of choices. Many students combine features from different charts that they find.

After 25 minutes, I have students who want to share their charts with the class display their work on my document camera. Students who are especially proud of their use of colors and artistic ability tend to share. On the surface, this is not an assignment that requires much problem solving or thinking. However, it sets the stage for the next activity in which students read how different parts of the electromagnetic spectrum interact with different materials. In addition, this provides students a good foundation for tomorrow's activity where they determine what materials block the electromagnetic waves produced by their mobile phones.

## How Electromagnetic Waves Interact with Matter

10 minutes

As students finish their charts they bring them up to me, I hand out the EM Spectrum and Interaction sheet and ask students to read about the source of electromagnetic waves and how the energy of the waves change with frequency and wavelength. They also read about the three ways that light interacts with matter; this includes some examples. Embedded in the reading are several questions that students answer to check their understanding of the material. Students have 10 minutes to complete this assignment which I collect at the end of the period. I use EM Spectrum and Interaction - Solutions to correct the sheets and assess student understanding. This assignment gives students the foundation knowledge needed for tomorrow's assignment, which is a laboratory activity where they test what materials block their mobile phone signal.

For homework, students are to search the internet to find two images of the same object as viewed from two different parts of the electromagnetic spectrum. I explain the homework with the Images Homework Power Point that provides a description and examples of what I want. They place their pictures in a Google Classroom folder I have created online. I ask students to include their sources.