Science · 1st Grade · Light and Sound Waves · Weeks 1-9

Communicating with Light

Students design and build devices that use light to send messages across a distance.

• Common Core State Standards
• 1-PS4-4
• K-2-ETS1-2

About This Topic

This topic brings together the science of light and the engineering design process by challenging students to use light as a tool for sending information. Standard 1-PS4-4 asks students to use tools and materials to design and build a device that uses light or sound to communicate over a distance, and this topic focuses on the light side of that challenge. Before smartphones and radio, people used signal fires, mirrors, semaphore flags, and lighthouses, all of which encode information in patterns of light.

Students work through the design cycle as defined in K-2-ETS1-2: sketching a plan, building a prototype, and testing whether their partner can correctly receive and decode the intended message. This requires both scientific thinking (what properties of light can I control?) and systems thinking (how do my partner and I agree on a shared code?).

Active learning is the engine for this topic. Students learn far more by building, testing, and revising their own signaling devices than by watching a demonstration. The natural feedback loop, when a partner does not understand a signal, creates a real engineering problem to solve through revision, which mirrors actual engineering practice in a way that is genuine and motivating for first graders.

Key Questions

1. Design a system to send a message using only light.
2. Evaluate the effectiveness of different light signals for communication.
3. Compare how light signals are used in everyday life for safety and information.

Learning Objectives

• Design a device using light to transmit a simple coded message to a partner.
• Demonstrate how to send and receive a message using a light signaling system.
• Compare the effectiveness of different light signals (e.g., flashing, steady beam) for clear communication.
• Identify everyday examples of light signals used for safety and information.

Before You Start

Properties of Light

Why: Students need a basic understanding that light travels and can be blocked or directed to build signaling devices.

Introduction to the Engineering Design Process

Why: Familiarity with the steps of designing, building, and testing is necessary for this hands-on challenge.

Key Vocabulary

signal	A sign or action that conveys information or a message.
code	A system of symbols or signals used to represent letters, numbers, or messages.
prototype	An early model or sample of a device built to test a concept or process.
transmit	To send something, like a message or signal, from one place to another.

Watch Out for These Misconceptions

Common Misconception

Light communication only works over very long distances.

What to Teach Instead

Some students think light signals are only for ships or airports. Pointing out everyday examples like a car's turn signal, a TV remote control using infrared light, or a notification LED on a device helps them see that light communication happens at all scales, including very short ranges.

Common Misconception

The light itself is the message, not the pattern of flashes.

What to Teach Instead

Young students can miss that it is the pattern of signals, not the presence of light, that carries meaning. Having them compare random flashing to a coded sequence and ask which one their partner could actually understand reinforces the idea that encoding a message requires agreed-upon structure.

Common Misconception

Brighter always means better communication.

What to Teach Instead

Students sometimes design signals that are simply very intense. Testing whether a super-bright but non-patterned signal successfully delivers information helps them understand that the structure of the signal matters more than its intensity for communication to work.

Active Learning Ideas

Inquiry Circle: Design a Flash Code

Pairs agree on a simple binary code such as one flash for yes and two flashes for no. They write four questions for their partner to answer using only flashes, then test from across the room and record how many answers were received correctly before refining their code.

30 min·Pairs

Simulation Game: Semaphore School

The teacher demonstrates a simplified card semaphore system: red card up means letter A, blue card up means letter B. Small groups practice sending and receiving three-letter words across the classroom, then discuss what made some signals easier to read than others.

20 min·Small Groups

Gallery Walk: Light Signals in the Real World

Post images around the room showing real light signals: a traffic light, a lighthouse, brake lights, an emergency vehicle light bar, and a crosswalk signal. Students walk around and write on sticky notes what message each signal sends and which group of people it is designed for.

20 min·Individual

Formal Debate: Which Signal Fits the Situation?

Present two contrasting scenarios: sending a message across a foggy field and sending a message in a noisy stadium. Small groups argue which situation calls for a light signal versus a different type of signal, backing their choice with evidence from their investigation.

25 min·Small Groups

Real-World Connections

• Lighthouses use powerful beams of light to guide ships safely at night, sending a clear signal to prevent them from running aground on shorelines.
• Traffic signals use different colored lights to control the flow of vehicles and pedestrians, communicating instructions to stop, go, or slow down.
• Morse code, historically sent using flashing lights or telegraphs, allowed for rapid communication over long distances before modern technology.

Assessment Ideas

Quick Check

Observe students as they test their light signaling devices. Ask: 'Can your partner understand your message? What part of your signal is confusing?' Note which students can identify a problem with their design.

Peer Assessment

After students have attempted to send a message, have them switch roles. The receiver should explain what they thought the sender's message was. The sender then states if the message was received correctly and suggests one change to make it clearer.

Exit Ticket

Provide students with a slip of paper. Ask them to draw one way light is used to send a message and write one sentence explaining how it works.

Frequently Asked Questions

How do traffic lights use light to communicate?

Traffic lights use color coding so drivers and pedestrians receive the same information without words. Red means stop, yellow means slow down, and green means go. The position of each color is also fixed, so people who have difficulty distinguishing colors can still read the signal by its location on the pole.

What is a lighthouse and how does it communicate?

A lighthouse is a tall tower with a very bright rotating light built near a rocky or dangerous section of shore. Each lighthouse flashes in its own specific pattern, so sailors can identify exactly which lighthouse they are seeing and know where they are on the water without any words or radio contact.

How can active learning help students design light communication devices?

The design-test-revise cycle puts students in the role of engineers solving a real problem. When a student's flash code fails to be understood by their partner, they have genuine motivation to improve it. This authentic feedback loop drives revision and builds persistence in a way that a hypothetical exercise simply cannot.

Is a TV remote an example of light communication?

Yes. TV remotes use infrared light, which our eyes cannot detect, to send coded signals to the TV. Each button produces a different pattern of flashes happening too fast to see, but the TV's sensor reads the pattern and responds. It is the same principle as a lighthouse, just invisible and much faster.