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Science lesson plan · 4th grade (Year 5 in England) · 45 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 · 5 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 crest is the top of a wave. (True / False) → TruePrompt: Two are points (top and bottom); two are distances (across and up).
  2. True or false? Amplitude is measured from the middle line, not from the trough. (True / False) → TruePrompt: Two are points (top and bottom); two are distances (across and up).
  3. True or false? Amplitude is the distance from crest to crest. (True / False) → FalsePrompt: Two are points (top and bottom); two are distances (across and up).

Hook · 5 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 · 10 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 · 10 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 long spring (slinky) on the floor, 2 complete waves fit into 18 cm. What is the wavelength? → 9 cmPrompt: Wavelength is the length of one complete wave.
  2. Two water waves have amplitudes of 9 cm (wave A) and 8 cm (wave B). Which carries LESS energy? (wave A / wave B) → wave BPrompt: Bigger amplitude means more energy.

You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 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 wavelength becomes zero. / The wave stops. / The amplitude gets bigger, so the sound is louder. / The amplitude gets smaller.) → The amplitude gets bigger, so the sound is louder.Prompt: A bigger pluck means a bigger vibration.
  2. In waves on a pond, 6 complete waves fit into 42 cm. What is the wavelength? → 7 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/ 8

  1. Question 1

    In a skipping rope being shaken, 6 complete waves fit into 30 cm. What is the wavelength?

    Answercm

  2. Question 2

    Two sound waves are drawn the same way. Wave A has an amplitude of 5 squares and wave B has 8 squares. Which is the LOUDER sound?

    • A. wave A
    • B. wave B

  3. Question 3

    A singer sings the same note quietly, then loudly. Which part of the sound wave changes?

    • A. nothing
    • B. the amplitude
    • C. the number of ears listening
    • D. the wavelength

  4. Question 4

    Two sound waves are drawn the same way. Wave A has an amplitude of 9 squares and wave B has 6 squares. Which is the LOUDER sound?

    • A. wave A
    • B. wave B

  5. Question 5

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

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

  6. Question 6

    In a long spring (slinky) on the floor, 3 complete waves fit into 24 cm. What is the wavelength?

    Answercm

  7. Question 7

    Two water waves have amplitudes of 3 cm (wave A) and 4 cm (wave B). Which carries LESS energy?

    • A. wave A
    • B. wave B

  8. Question 8

    Why are storm waves at the beach dangerous?

    • A. They move more slowly than small waves.
    • B. They have no energy.
    • C. They are made of a different liquid.
    • D. Their large amplitude means they carry a lot of energy.

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Answer key: Measure and compare waves: amplitude and wavelength

  1. 1. 5 cm

  2. 2. B. wave B

  3. 3. B. the amplitude

  4. 4. A. wave A

  5. 5. B. The amplitude gets bigger, so the sound is louder.

  6. 6. 8 cm

  7. 7. A. wave A

  8. 8. D. Their large amplitude means they carry a lot of energy.