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Science lesson plan · 4th grade (Year 5 in England) · 30 minutes

Measure and compare waves: amplitude and wavelength

Light, sound and waves

CCSS NGSS.4-PS4-1England: KS3 Physics: Waves (observed waves)

Objective and success criteria

Students will: Measure and compare waves: amplitude and wavelength.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Parts of a wave: crest, trough, amplitude and wavelength

Leads to: the next skill in this area.

Materials: Slinky or rope, Mirrors and torches, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Parts of a wave: crest, trough, amplitude and wavelength). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. True or false? The trough is the highest point of a wave. (True / False) → FalsePrompt: Two are points (top and bottom); two are distances (across and up).
  2. True or false? Wavelength is the height of a wave. (True / False) → FalsePrompt: Two are points (top and bottom); two are distances (across and up).
  3. True or false? Wavelength is measured from one crest to the next. (True / False) → TruePrompt: Two are points (top and bottom); two are distances (across and up).

Hook · 3 min

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

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: In a long spring (slinky) on the floor, 5 complete waves fit into 45 cm. What is the wavelength?
  • Step 1: 45 ÷ 5 = 9
  • Step 2: So the answer is: 9 cm
  • Answer: 9 cm
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. In a skipping rope being shaken, 6 complete waves fit into 18 cm. What is the wavelength? → 3 cmPrompt: Wavelength is the length of one complete wave.
  2. Two water waves have amplitudes of 6 cm (wave A) and 3 cm (wave B). Which carries LESS energy? (wave A / wave B) → wave BPrompt: Bigger amplitude means more energy.

You do: independent practice · 7 min

  • 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.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A guitarist plucks a string harder. What changes in the sound wave? (The amplitude gets bigger, so the sound is louder. / The amplitude gets smaller. / The wave stops. / The wavelength becomes zero.) → The amplitude gets bigger, so the sound is louder.Prompt: A bigger pluck means a bigger vibration.
  2. In a long spring (slinky) on the floor, 2 complete waves fit into 12 cm. What is the wavelength? → 6 cmPrompt: Wavelength is the length of one complete wave.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Parts of a wave: crest, trough, amplitude and wavelength.
  • Use concrete materials: slinky or rope.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

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

Free lesson plan from eurekami.com/lesson-plan-builder

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Measure and compare waves: amplitude and wavelength

Name

Date

Score/ 6

  1. Question 1

    Two water waves have amplitudes of 7 cm (wave A) and 4 cm (wave B). Which carries LESS energy?

    • A. wave A
    • B. wave B

  2. Question 2

    In a skipping rope being shaken, 4 complete waves fit into 28 cm. What is the wavelength?

    Answercm

  3. Question 3

    A guitarist plucks a string harder. What changes in the sound wave?

    • A. The amplitude gets bigger, so the sound is louder.
    • B. The wavelength becomes zero.
    • C. The amplitude gets smaller.
    • D. The wave stops.

  4. Question 4

    Two water waves have amplitudes of 2 cm (wave A) and 4 cm (wave B). Which carries LESS energy?

    • A. wave A
    • B. wave B

  5. Question 5

    In a long spring (slinky) on the floor, 4 complete waves fit into 8 cm. What is the wavelength?

    Answercm

  6. Question 6

    Two water waves have amplitudes of 6 cm (wave A) and 8 cm (wave B). Which carries LESS energy?

    • A. wave A
    • B. wave B

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Answer key: Measure and compare waves: amplitude and wavelength

  1. 1. B. wave B

  2. 2. 7 cm

  3. 3. A. The amplitude gets bigger, so the sound is louder.

  4. 4. A. wave A

  5. 5. 2 cm

  6. 6. A. wave A