• Quick retrieval from earlier learning (Parts of a wave; How sound travels through solids, liquids and gases). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Astronauts on a spacewalk talk by radio. Why can't they just shout? (Space is a near vacuum, so sound cannot travel between them / Their voices are too quiet / Radio waves are a type of sound / Space is too cold for sound) → Space is a near vacuum, so sound cannot travel between themPrompt: Radio waves are electromagnetic waves.
2. 20 waves pass a point in 4 seconds. What is the frequency, in hertz (Hz)? → 5 HzPrompt: Frequency is the number of waves per second.
3. An alarm clock rings inside a jar. As the air is pumped out, the ringing gets quieter. Why? (Sound needs particles to travel through, and there are fewer left / Air makes sound quieter / The clock stops ringing / Glass absorbs all sound) → Sound needs particles to travel through, and there are fewer leftPrompt: Can sound travel through a vacuum?

• Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
• Share the objective: Transverse and longitudinal waves. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Is this a transverse or a longitudinal wave: seismic P waves?
• Step 1: In longitudinal waves, vibrations are parallel to the direction the wave travels.
• Step 2: So the answer is: longitudinal
• Answer: longitudinal
• 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. Is this a transverse or a longitudinal wave: a slinky pushed and pulled along its length? (transverse / longitudinal) → longitudinalPrompt: Compare the direction of vibration with the direction the wave travels.
2. On a wave diagram, what is the wavelength? (the time for one wave / the distance from one point to the same point on the next wave, such as crest to crest / the height of a crest / the number of waves per second) → the distance from one point to the same point on the next wave, such as crest to crestPrompt: It is a length, measured in metres.

• 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. Is this a transverse or a longitudinal wave: sound? (transverse / longitudinal) → longitudinalPrompt: Compare the direction of vibration with the direction the wave travels.
2. On a wave diagram, what is the wavelength? (the number of waves per second / the height of a crest / the distance from one point to the same point on the next wave, such as crest to crest / the time for one wave) → the distance from one point to the same point on the next wave, such as crest to crestPrompt: It is a length, measured in metres.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.