• Quick retrieval from earlier learning (Send messages with light and sound). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Does this signal use light, sound or both: a doorbell? (light / sound / both light and sound) → soundPrompt: Do you see it, hear it, or both?
2. Ships at sea at night watch for a lighthouse. What message does its light send? (It is time for dinner. / Danger: rocks or land are near here. / Fish are nearby. / The sea is warm today.) → Danger: rocks or land are near here.Prompt: Why would a ship need to know where the coast is?
3. What message does this signal send: a red traffic light? (Stop and wait. / The car is about to turn left. / There may be a fire: get out. / Playtime is over; go back to class.) → Stop and wait.Prompt: Where would you meet this signal, and what should you do?

• Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
• Share the objective: Send and decode messages using patterns. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: A torch (flashlight) flashes short (•) and long (–) pulses. Use the key to decode the message. Key: D = –•• O = ––– G = ––• Message: –•• / ––– / ––•
• Step 1: –•• → D, ––– → O, ––• → G
• Step 2: So the answer is: DOG
• Answer: DOG
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. A torch (flashlight) flashes short (•) and long (–) pulses. Use the key to decode the message. Key: S = ••• T = – A = •– R = •–• Message: ••• / – / •– / •–• → STARPrompt: Each group between the slashes is one letter.
2. In Morse code, MOON is sent as –– / ––– / ––– / –•. How many flashes (dots and dashes) is that altogether? → 10Prompt: Count the symbols for each of the 4 letters.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Why are digital messages less likely to be spoiled by noise than older signals? (Noise cannot travel through air. / They use no energy. / Digital messages are louder. / Each part is only on or off, so small changes are easy to ignore or correct.) → Each part is only on or off, so small changes are easy to ignore or correct.Prompt: Is it easier to tell "on" from "off" or to tell small differences in loudness apart?
2. In Morse code, TREE is sent as – / •–• / • / •. How many flashes (dots and dashes) is that altogether? → 6Prompt: Count the symbols for each of the 4 letters.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-4.