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# Lesson Plans

## Electromagnetic Energy and Its Spectrum

Author: Joyce Brumberger
Source: Original

#### Abstract

As a result of hands-on exploration and inquiry, students will learn about electromagnetic radiation and the electromagnetic spectrum. Students will create waves to understand the relationship between energy and wavelength. Students will design and implement an experiment to reduce UV exposure to an object.

#### Objectives

What should students know as a result of this lesson?

• electromagnetic radiation is solar or light energy
• electromagnetic radiation travels in waves through the vacuum of space to the Earth
• electromagnetic radiation contains different frequency types and therefore different wavelengths of energy
• the electromagnetic spectrum classifies the frequency types by their wavelengths
• long wavelengths carry less energy than short wavelengths

What should the students be able to do as a result of this lesson?

• relate amounts of energy to their wavelengths
• use a prism to see the spectrum of visible light
• design and implement an experiment to reduce UV exposure to an object

#### Materials

Engagement:

• Working radio or cell phone
• Microwave oven
• Hot plate and TV remote (works off of infrared beam)
• Flashlight or lamp
• UV beads (can be purchased from Education Innovations, Inc. 888-912-7474, \$6.95/pkg of 250)
• X-ray photograph
• Toy space gun - "ray gun"

Exploration:

Per Group:

• 1 plastic shoe box
• Water
• Flashlight
• Prism
• 15-20' nylon rope, 1 cm diameter or more

Elaboration:

• 30 UV beads in a snack size zip lock bag/group

• Suntan lotions of varying SPF's
• Sunglasses or sunglass lenses, polarized and non-polarized
• Cellophane of varying colors including clear
• Plexiglas samples, any size or shape
• Transparent plastic lids and containers, varying colors
• Glass of varying colors
• Various types of fabric

Preparation:

• Display items for Engagement phase in an area where students can walk around and observe them
• Fill plastic shoe box half full of water.
• Fill snack size zip lock bags with 30 beads - 1 bag per group

#### Procedures

Engagement

1. Gather the following items and put them on a display table:
1. Radio that is playing or a cell phone
2. Microwave oven
3. A glowing hot plate and a TV remote
4. Flashlight or lamp that is switched on
5. Two small packages of UV beads - one not exposed to sunlight, one that is (must be done immediately before displaying)
6. An X-Ray photograph
7. Toy space gun - "ray gun"
2. Ask students, "What do you think all these things have in common?"
3. Divide students into groups of three.
4. Instruct groups to observe and brainstorm the question together.
5. Provide each group with a poster size sheet of paper and a marker and tell them to write all their ideas on the paper.
6. Instruct each group to hang their paper on the wall or other designated area.
7. Ask one member from each group to explain their group's ideas.
8. Ask the group as a whole their consensus of what these items have in common and have a volunteer record the ideas on another sheet of poster size paper to be hung.
9. Do NOT provide any answers at this time.

Assessment: Assessment is ongoing as students write and verbally discuss their thoughts and ideas.

Exploration

1. Provide each group of students a shoebox plastic container 1/2 filled with tap water.
2. Instruct students that they are going to carefully observe what happens when someone knocks on the short side of the container.
3. Tell students that the process will be repeated, letting the water settle between knocks, until everyone can illustrate the patterns they see in their notebook.
4. Tell the group to select one person to knock on the box and begin.
5. When illustrations are complete, tell the student knocking on the side to do it harder, without spilling the water.
6. Instruct the groups to repeat as necessary until they can illustrate the patterns in their notebook.
7. Instruct students to select one person to put their mouth on the short side of the box and make a soft sound.
8. Again, instruct the groups to observe water patterns and illustrate them in their notebooks.
9. Tell the groups to repeat with the individual making loud sounds.
10. Tell the third student in the group to place their index finger in the water on the short side of the box and push the water gently.
11. Instruct students to illustrate the surface patterns of the water.
12. Tell students to repeat the procedure but to flick the water with more force once again noting surface patterns and illustrating.
13. Using a long rope on a smooth surface, ask two students to hold either end of the rope and gently pull it taut.
14. Instruct one student to create a flat wave with the rope on the floor by moving their hand back and forth.
15. Tell students to notice the size of the wave.
16. Tell the student moving the rope to repeat doing it with more energy and then again with less energy.
17. Instruct students again to note the size of the wave.
18. The teacher will assess the number of times to repeat the exercise so that everyone has a clear understanding.
19. Instruct students to record their observations in their notebooks.
20. Provide each group with a flashlight and prism. Instruct each group to designate one of the students to shine the flashlight directly towards the prism from a short distance away, one to hold a white sheet of paper behind the prism, and the other to record the observations the group makes on the sheet of paper.

Assessment: Assessment is ongoing as the students verbally discuss their observations and record them in journals.

Explanation

Ask and discuss the following questions and concepts with students:

• Describe the patterns in the surface of the water when the side of the container was knocked gently and then when it was knocked harder.

Answers will vary, but observations would be that waves started on the disturbed side of the box and spread out as it traveled to the other side of the box. The waves then started to return in the opposite direction. The size of the waves was smaller when the box was knocked harder.

• Describe the patterns in the surface of the water when someone made soft and loud sound next to the box.

The water vibrated with waves. The louder the sound, the smaller the waves.

• Describe the patterns in the surface of the water when someone pushed it with their finger first gently then with more force.

Waves were formed and once again the large waves were formed with a gentle push and small waves were formed with a harder force.

• Compare the pattern of waves with the rope when the rope was shook gently and then with more energy.

The harder the rope was shook, the smaller the wavelength.

• There are different kinds of energy and one kind of energy can be changed to another. For example, the energy from the person shaking the rope was transferred to the rope. We can often see the effects of energy, but not the energy itself. Based on what you did today, what do you think is one way in which energy from the sun reaches the Earth?

One way energy from the sun reaches the Earth is in waves.

• Solar Energy, called electromagnetic radiation, travels through the vacuum of space in waves of energy, as well as packets of energy called photons. As it reaches the Earth, the atmosphere and clouds reflect some of that energy back into space, they absorb some of it, the Earth's surface absorbs about 1/2 of the energy, and some of the energy is reflected off the surface from the ocean and ice. Recall the lesson "The Bending and Bouncing of Light" which demonstrated how light is reflected.
• One form of energy that we receive from the sun allows us to see. What is that form of energy called?

Visible light

• Describe what happened to the visible light from the flashlight when you used a prism.

The white light waves were bent as they went through the prism revealing a spectrum of colors in the order of ROYGBIV - red, orange, yellow, green, blue, indigo, and violet. The red color emits long wavelengths and the violet colors emit shorter wavelengths.

• Which colors have the highest energy in the visible light spectrum?

The colors blue, indigo, and violet have more energy and therefore emit short wavelengths.

• Rainbows are a result of seeing visible light bent to reveal the colors that travel together unseen. Are there other forms of solar energy that we cant see?

Yes. Energy coming from the sun is called electromagnetic radiation and the various forms of energy are organized into an electromagnetic spectrum. Just like the light spectrum, the different forms of energy are organized with longer energy waves on one side and shorter energy waves on the other side. Let's look back at the items that are on the display table and the order in which they were presented. All the items represent a form of electromagnetic radiation. The Teacher should discuss the items based on the chart below.

Longest Wavelengths ->Shortest Wavelengths

 Radio Waves Microwaves Infrared Radiation Visible Light ROYGBIV Ultraviolet Light X-Ray Gamma Rays

Lower Energy -> Higher Energy

Assessment: Assessment continues as students respond to questions and ask appropriate questions reflecting their degree of understanding.

Elaboration

1. Divide students into groups of three.
2. Tell students long term exposure to ultraviolet radiation is harmful to human and other animal skin.
3. Provide each group with a package of UV beads and instruct them to design and implement as many tests as possible to find ways that will inhibit or reduce UV exposure to the beads.
4. Instruct students to brainstorm together and write a procedure for experimentation and a list of materials needed.
5. Instruct students to develop a qualitative rating scale to use when determining the effectiveness of their plan.
6. Instruct one member of the group to give you the list and provide them with as many materials available.
7. Tell students that any plans for which materials are unavailable can be completed outside at home.
8. Allow all reasonable experimentation plans of experimentation and tell students to record their findings.
9. Ask one member of each small group to report and discuss their findings with the whole group.

#### Prerequisites

The Bending and Bouncing of Light Lesson (not necessary but very helpful)

#### Best Teaching Practices

• Learning Cycle
• Inquiry
• Science Process Skills

#### Alignment with Standards

NGSS Standards:

• MS-PS4-1 Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave.
• MS-PS4-2 Develop and use a model to describe that waves are reflected, absorbed, and transmitted through various materials.

Common Core Standards:

• RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts.
• RST.6-8.3 Follow precisely a multi-step procedure when carrying our experiments, taking measurements, or performing technical tasks.
• WHST.6-8.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.

National Standards:

• Grades 5-8 Content Standard A
• Grades 5-8 Content Standard B
• Grades 5-8 Content Standard E
• Grades 5-8 Content Standard F

Ohio Standards:

• Grades 5-8 Physical Science Benchmark C
• Grades 5-8 Earth and Space Sciences Benchmark C
• Grades 5-8 Scientific Ways of Knowing Benchmark A
• Grades 5-8 Scientific Inquiry Benchmark A

#### Content Knowledge

Energy from the sun travels through the vacuum of space at the speed of light to Earth in waves of varying frequencies. This energy is referred to as electromagnetic radiation because it has electric and magnetic elements to it. The varying frequencies of solar energy are explained by the electromagnetic spectrum, which organizes the frequency types based on wavelength, which are measured in nanometers. The longer the wavelength the less energy the wave carries, the shorter the wavelength the higher the energy. The electromagnetic spectrum is displayed in the chart below.

Longest Wavelengths ->Shortest Wavelengths

 Radio Waves Microwaves Infrared Radiation Visible Light ROYGBIV Ultraviolet Light X-Ray Gamma Rays

Lower Energy -> Higher Energy

As electromagnetic energy reaches the Earth, 26% of it is reflected by clouds and the atmosphere, 19% is absorbed by the atmosphere and clouds, 4% is reflected off the Earth from ocean surfaces and ice, and the remaining 51% is absorbed by the Earths surface. As ice melts, less energy is reflected and more energy can be absorbed by the surface of the Earth. This is common with seasonal changes, but if ice continues to melt it could be another contributing factor to global warming.

Two excellent web sites for more detailed information regarding the electromagnetic spectrum are http://science.hq.nasa.gov/kids/imagers/ems/ and http://www.pbs.org/wgbh/nova/gamma/spectrum.html

#### Safety

Do not shine flashlight in eyes

#### Applications

Life on Earth is primarily dependent on the sun for its source of energy. Generally, people know this energy to be heat and light, but there are other components that are not well understood or misunderstood. Electromagnetic radiation is commonly called solar energy and is comprised of many frequency types such as radio waves, microwaves, infrared waves, visible light, UV light, X-rays, and gamma rays. All of these forms of energy are usable in our daily lives and has its benefits and its risks. Exploring the benefits and minimizing the risks in utilizing this energy can best be done by individuals who are informed and knowledgeable. As we continue to look to the sun as an alternative source of energy, it is necessary to understand what that source truly provides.

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#### Other Considerations

Grouping Suggestions: Try to insure that all students have participated and expressed their ideas either verbally or through written comments. When working in pairs or groups try to make the groups as heterogeneous as possible being sensitive to specific needs of individuals.

Pacing/Suggested Time: Engagement: 10 minutes, Exploration: 15 minutes, Explanation: 15 minutes, Elaboration: 30-35 minutes

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