• 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? (Their voices are too quiet / Radio waves are a type of sound / Space is a near vacuum, so sound cannot travel between them / Space is too cold for sound) → Space is a near vacuum, so sound cannot travel between themPrompt: Radio waves are electromagnetic waves.
2. 50 waves pass a point in 5 seconds. What is the frequency, in hertz (Hz)? → 10 HzPrompt: Frequency is the number of waves per second.
3. In which direction do air particles vibrate when a sound wave passes? (backwards and forwards, parallel to the direction the sound travels / in circles / up and down, at right angles to the wave / they do not move) → backwards and forwards, parallel to the direction the sound travelsPrompt: Sound is a longitudinal wave.

• 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: ripples on a pond? (transverse / longitudinal) → transversePrompt: Compare the direction of vibration with the direction the wave travels.
2. Which kind of wave can travel through a vacuum? (electromagnetic waves such as light / seismic waves / water waves / sound waves) → electromagnetic waves such as lightPrompt: Sunlight crosses space to reach us.

• 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 8 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. On a wave diagram, what is the wavelength? (the height of a crest / the number of waves per second / the time for one wave / the distance from one point to the same point on the next wave, such as crest to crest) → 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.
2. Types of wave: which statement is NOT true? (All electromagnetic waves are transverse. / Light is a longitudinal wave. / Sound waves are longitudinal. / Waves transfer energy without transferring matter.) → Light is a longitudinal wave.Prompt: Which kind of wave is light?

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