---
title: "Communication with Light & Sound"
description: "Design and build a device that uses light or sound to solve the problem of communicating over a distance"
canonical: https://lightmysky.com/learn/science/communication-with-light-and-sound-mt_ZL9qVVnpwN
source: https://lightmysky.com/learn/science/communication-with-light-and-sound-mt_ZL9qVVnpwN.md
retrieved: 2026-10-19
---

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# Communication with Light & Sound

Design and build a device that uses light or sound to solve the problem of communicating over a distance

Subject: Science · Area: Waves, Light & Sound · Ages 6 to 7
Page: https://lightmysky.com/learn/science/communication-with-light-and-sound-mt_ZL9qVVnpwN

## Ready when they can

- Design a device that uses light or sound to communicate over a distance (e.g. string telephone, torch signals)
- Build and test the device, identifying what works and what could be improved
- Explain how the device uses properties of light or sound to transmit information

## Lesson: Sending messages with light and sound

You have learned that torches make light and vibrating things can make sound. Use either to send a message across a distance. A torch uses flashes. A string telephone uses your voice. Before using flashes, both people must agree what each pattern means.

**Example.** Ask an adult to make a small hole in the bottom of each paper cup. Thread string through the holes and tie knots inside. Two people gently pull the string tight. One speaks into a cup while the other listens. Speech makes the first cup vibrate. Vibrations travel along the string to the second cup.

*(drawing: The second cup vibrates and makes sound that your friend can hear.)*

Test your telephone with a short message. Ask your friend to repeat what they heard. A loose string usually carries speech poorly. Compare loose and tight string while keeping the cups, message, distance and voice the same. Changing only string tightness helps you find whether it made a difference.

A torch makes its own light, so its flashes can be seen at night. Keep a clear path to your friend. If flashes are hard to see, move closer and test again. Use a small battery torch below face level. Never use a laser. Count each flash once and skip the pauses.

*(drawing: Agree that this pattern means 'come here'. The pause separates flashes; it is not a flash.)*

**Recap.** Cup and string vibrations can carry speech. Torch flashes can carry an agreed message. Test whether your friend receives the message.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Light & seeing in the dark](https://lightmysky.com/learn/science/light-and-seeing-in-the-dark-mt_4i-FKXDDXh)
- [Vibrations & sound](https://lightmysky.com/learn/science/vibrations-and-sound-mt_VBl1T1sFCM)

## Opens up

- [Patterns & Codes for Information](https://lightmysky.com/learn/science/patterns-and-codes-for-information-mt_n5_Jt4ExUd)