Early Warning Systems

Think about a street signal light. What does the green light mean for a driver? A green light tells the driver that he or she can drive through an intersection. It implies that drivers at the adjacent lights are stopped and waiting for their lights to turn green. In other words, light can tell us about certain conditions in the world around us. Warning lights come in a variety of colors and types depending on the intended purpose and where they are used. In this unit, students learn about the use of warning lights in the U.S. and in other countries. They build simple models and investigate: 1) how everyday objects emit different wavelengths of light, 2) relative transmission of light through materials, 3) reflective properties of materials. The unit engages students in discussions, web resources and activities that prepare them for a culminating design challenge, where they use their knowledge gained from the lessons to design an adjustable early warning device that transmits light across a distance. Students develop a presentation explaining the use and purpose of their early warning device.

Educational Outcomes

  • Students research the international use of warning light colors
  • Students describe colors of light in terms of their relative wavelengths and frequencies
  • Students investigate different amounts of light transmission through fatty food samples
  • Students investigate the reflective properties of materials to strike a target with a laser
  • Students engage in a design challenge to build a light-based early warning system

STEAM Integration

Students access different sources of information on warning lights, the properties of light and the electromagnetic (EM) spectrum, and the reflection and transmission of light through different materials. They leverage digital tools, apply scientific concepts and skills and build models to demonstrate their conceptual understanding and skill proficiency. The design challenge brings students through the engineering design process and allows for an integrated approach to addressing the design prompt, where students apply multiple STEAM skills and principles.


NGSS MS-PS4-2: Develop and use a model to describe that waves are reflected, absorbed, and transmitted through various materials.

NGSS MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Unit Materials

This unit can be completed using the RAFT Makerspace-in-a-Box kit. The kit contains many items with various attributes useful for different purposes by students. Examples include rigid items for structure such as craft sticks, plastic rods, and cardboard tubes; flexible/cuttable items such as foam, chenille stems, straws, and cardstock for making customized structures; and items serving as connectors such as paper clips, binder clips, and stickers/tape. Note: Some lessons call for additional items not included in the kit. We encourage facilitators to be creative and provide other materials to explore in the lessons. Questions? Email us: education@raft.net

Maker Journal Pages

Students record their learning in Maker Journal pages, sheets containing tasks and prompts specific to each lesson in the unit, including the culminating design challenge. These sheets encourage students to reflect on their learning throughout the unit and can be used as part of a larger student portfolio with which to demonstrate growth in concept knowledge and design skills. These sheets can be copied for students or recreated by students in a bound notebook.

Tips for an Active Classroom

Communication is critical in the design process. Students need to be allowed to talk, stand, and move around to acquire materials. Help students become successful and care for the success of others by asking them to predict problems that might arise in the active environment and ask them to suggest strategies for their own behavior that will ensure a positive working environment for all students and teachers.

Design Thinking

Our integrated STEAM units incorporate a non-linear design thinking model, with each phase being repeatable to allow students to rework and iterate while developing a deeper understanding of the core concepts. The phases of the design thinking model are:

Empathize: Work to fully understand the experience of the user

Define: Process and synthesize findings from empathy work to form a user point of view

Ideate: Explore a wide range and variety of possible ideas for solutions

Prototype: Transform ideas into a physical form with which to learn and interact

Test: Refine prototypes, learn more about the user, and refine original point of view

Lesson 1: Conveying Meaning Using Light (45 minutes)

Students develop empathy by learning how other countries convey warnings to their citizens using lights and then make comparisons with warning light usage in the United States. They create a handy reference chart that compares usage between four countries of their own choosing, allowing them to identify patterns between colors, styles, and conventions in warning lights and the intended use for each particular color or style.

Learning Target

  • Students will be able to develop a reference chart as a model to describe that light can be transmitted in different colors to convey specific information.

Essential Questions

  • How do other countries convey warning messages using lights?
  • How do the meanings for specific color warning lights in the U.S. compare to those in other countries?



  1. Show students images of different emergency warning lights. You may want to select images from a Google image search on the topic.
  2. Students choose and record the names of four (4) different countries in the lesson Maker Journal.
  3. Students find websites containing information on warning lights for each country AND the United States. They may start with the web resources listed in the materials section above. 
  4. Students complete the table in the Maker Journal. This serves as a reference chart.
  5. Students use the reference chart to describe why each color of warning light is well-suited for its function in conveying a specific meaning.

Sample teacher and student dialog

T: “What is the purpose of different kinds of lights? Is there a special use for each color? What do they mean?”

S: “Police use red and blue, they tell drivers to move to the side of the road!”

T: “We are going to conduct web research to find out more about the purpose of different colors of emergency/warning lights used in the U.S. and four different countries. Where might you find this information?”

S: “Wikipedia, Google search, resources in the library”

T: “These are all good sources of information. Remember to use the rule of three, where you compare three sources of information on a topic to check for consistency. Use your Maker Journal page to record your findings.”


Conduct a whole group discussion to allow all students to share, discuss and compare their findings around different designs and uses for warning lights.

Lesson 2: EM Spectrum Bracelets (30-45 minutes)

Most students think of light only in terms of visible light, which we can observe directly with our eyes. The electromagnetic (EM) spectrum contains other forms of light such as infrared and x-rays, and these forms differ in the amount of energy they carry, their wavelengths, and their frequencies. Students assemble a bracelet as a model of the EM spectrum that serves as a mnemonic device that helps them remember the order of the types of light along the spectrum. They conduct research to identify devices/applications for the wavelengths represented in the EM spectrum.

Learning Targets

  • Students will be able to assemble a model of the EM spectrum
  • Students will be able to identify devices and applications for the wavelengths on the EM spectrum

Essential Questions

  • What is the structure of the EM spectrum?
  • How is the frequency of a light wave related to its wavelength?


  • Pipe cleaners, black
  • Pony beads in these colors: Black (1), red (1), orange (1), yellow (1), green (1), blue (1), dark blue (1), violet (1), UV sensitive (1), glow-in-the-dark (1), clear (3)
  • Pen or pencil
  • Internet access
  • Computer and/or mobile device
  • Web resources: Forensic Light Applications | Uses of Radio Waves | Microwaves


  1. Students use the spectrum chart in the lesson Maker Journal to individually assemble their spectrum bracelets.
  2. Students conduct web research to find information on devices or specific uses for each wavelength range represented in the spectrum.
  3. Students record their findings and answer and discuss questions in the lesson Maker Journal.

Sample teacher and student dialog

T: “What do you think radio waves look like? Can we see them? Do they have color? How do you know?”

S: “They are white, radio waves are invisible, they are grey!”

T: “We’ll build a model of the electromagnetic (EM) spectrum. This is a representation of all types of light waves, even the ones we can’t see. Afterwards we’ll do web research to find information on different uses for each type of light. The different types of light are based on the wavelength for each light wave type. Remember to use your Maker Journal to record your findings.”

S: “Light is based on energy!”


Hold a class discussion around the uses for each wavelength of light represented in the spectrum. Discuss the arrangement of light along the spectrum in terms of wave properties (amplitude, frequency, wavelength).

Lesson 3: Using Light to Trim the Fat (30 minutes)

Students conduct an investigation where they observe the transmission of light through paper treated with different food samples, each containing various amount of fat. Students explain the relative amounts of translucence in terms of the fat content in the samples and how it allows light to be transmitted through the paper. Then students develop a hypothesis for how the investigation can be used to help people make healthier food choices.

Learning Target

  • Students will be able to investigate the fat content in different foods and use the results as a model to describe that light waves are transmitted through certain materials.

Essential Question

  • How can investigating the amount of light transmitted through a material be useful for improving your health?


  • Pen/pencil
  • Marker
  • Small cups, 2 oz.
  • Cotton swabs
  • Food samples for testing
  • Paper towels or napkins


  1. Make sure students have a copy of the lesson Maker Journal, especially page 3 (data table).
  2. Show students examples of condiments such as butter, cooking oil, ketchup, mustard, or low-fat salad dressing. Ask students to predict the amount of light that might pass through each and how they would investigate it.
  3. Arrange food samples in a location safely accessible to all students. Food suggestions: ketchup, butter, mustard, cooking oil, dish soap, sour cream, soy sauce.
  4. Students follow the simple investigation procedure outlined in the lesson Maker Journal.
  5. Students answer questions and discuss their findings in a group discussion.

Sample teacher and student dialog

T: “If we were to shine a light on these foods, which one(s) do you think would allow the most light to shine through? How might we figure this out?”

S: “The cooking oil is more clear, butter blocks the light like a wall does.”

T: “We are going to conduct an investigation to see how much light can pass through various food samples. Then we will determine which food sample has the most fat in it based on the results. Finally, you will develop a hypothesis for how conducting an investigation like this can help you make healthier food choices.”

S: “Will you give us the samples?”

T: “The food samples are located in the designated area (you define this). Follow the instructions in your Maker Journal. I’ll circulate to answer questions and provide assistance as needed.”


Conduct a whole group discussion to allow all students to share their responses to the analysis questions and discuss different applications of this investigation to improve health and inform personal food choices.

Lesson 4: Bouncing the Beam! (30 minutes)

Students build a hinged mirror to explore the effect of geometry on reflected light in terms of the virtual images seen in the mirror. Then students investigate the reflective properties of different materials by reflecting a laser beam around obstacles in order to strike a target.

Learning Targets

  • Students will be able to use a hinged mirror as a model to describe the reflection of light in terms of geometry.
  • Students will be able to reflect a laser beam, strike a target and then describe the beam’s path.

Essential Questions

  • How does geometry affect the way light waves are reflected?
  • How can materials be used to transmit reflected light to an intended target?



  1. Make sure all students have safe and equal access to the materials. This activity requires space. Consider moving furniture to optimize the available space for students to safely work.
  2. Review the web resources together as a class or have students access them individually. Ask questions to clarify or expand on points of interest expressed by the students (see sample dialog for ideas).
  3. Students cut some reflective material into equal size sheets and tape them together, forming a hinged mirror.
  4. Students put an object in front of the hinged mirror. Using the lesson Maker Journal as a guide, they observe and record the number of images seen in the mirror for each angle measure.
  5. Students gather materials, sketch and build the laser course, and adjust the design until the laser beam reflects from several materials and reaches a specified target.
  6. Student groups discuss, compare and demonstrate their laser course designs.

Sample teacher and student dialog

T: “What is happening to the light beam? What is it about the surface of the object that causes this to happen?”

S: “It’s being reflected, the light is bending, reflecting the light instead of absorbing it.”

T: “Today we’ll explore these ideas by making a hinged mirror kaleidoscope that can bend at different angle measurements. Then we’ll design a “laser obstacle course” to make a laser beam change direction and hit a target. How might this help in the real world?”

S: “A car might need to be warned about a hazard before turning a corner.”

T: “Great idea! You will incorporate several reflective surfaces in your design, moving and adjusting them until the laser beam strikes the target that you must place at the end of the course. Let’s get to work!”


Student groups discuss and compare their laser beam courses and steps for striking the target.

Design Challenge: Early Warning Device (45-60 minutes)

Students demonstrate their knowledge of reflection, absorption and transmission of light waves by designing, building and testing an adjustable early warning device that transmits light across a distance. They engage in the design process multiple times until their device meets the defined criteria and constraints. Students develop a presentation describing how their light-based warning device can be used in the countries they researched in the first lesson.

Design Prompts

  • Build a device with an adjustable light beam that reflects, absorbs and/or transmits light to convey an early warning message to users across a distance.
  • Identify the countries that are most likely to use your device.


    1. Present and explain the design prompt(s) for the challenge (above)
    2. Review and define the criteria and constraints listed below and these terms: iteration, prototype. Alternatively, you can define them together as a class, providing students with voice and choice.
    3. Assign student teams or assign students to specific groups.
    4. Students follow steps in the design process and record their progress in the challenge Maker Journal.
    5. Students share and compare their design solutions, reflect on the data collection/calculations, and provide peer feedback for improvement on future iterations.

    The criteria and constraints for this challenge are listed below. Criteria are the requirements for the design or its expected functions or abilities. Constraints are limitations on the design such as time, space, available materials, money, etc. The criteria and constraints are also listed in the Maker Journal for this challenge.

    Criteria & Constraints

    • Device uses specific colors of light
    • Device includes components for reflecting, absorbing and/or transmitting light
    • Device includes adjustable light beam
    • Device built with materials provided
    • Device completed and tested in the given time
    • Device includes 8 or more different materials
    • Device can convey warning message from at least 20 feet away

    Ideate Phase

    During the ideation phase students should have ample time to discuss and research their ideas and potential impact. All ideas are welcome during the ideation phase, and students should be encouraged to think big. Students should capture their ideas using the Maker Journal or a digital tool (Google doc, other). Keep in mind students may return to this phase as many times as needed.

    Prototype Phase

    Students select one of the designs from the ideation stage to create using various materials. Initially they will have a rough prototype of the design that should eventually get better as they test it and make refinements. Students may also want to experiment with solutions that focus on changes in behavior. In this case encourage them to create a detailed plan as well as a device that will help to remind them or encourage this change in behavior. Students use the Maker Journal to draw and label their designs. Students may need to return to this phase as they iterate.

    Test Phase

    Students self evaluate as they test their designs in the Maker Journal. This activity should be focused on brevity and conducted at a brisk pace. Students should be going through ideas, building prototypes and evaluating their designs for at least three or four design cycles. Build time should be quick and designs should be kept simple. Students may return to this phase as they iterate.


    Students discuss and compare their solutions and give each other feedback on the ability of their design to transmit a light-based early warning message across a distance. Students also give suggestions for improvements to the design for future iterations. During the presentations, help students focus their thinking on the data collected and interpreting the results to better define the design prompts.