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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? Amplitude is the distance from crest to crest. (True / False) → FalsePrompt: 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? The crest is the top of a wave. (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, 3 complete waves fit into 6 cm. What is the wavelength? → 2 cmPrompt: Wavelength is the length of one complete wave.
  2. Two sound waves are drawn the same way. Wave A has an amplitude of 9 squares and wave B has 7 squares. Which is the LOUDER sound? (wave A / wave B) → wave APrompt: 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 singer sings the same note quietly, then loudly. Which part of the sound wave changes? (the number of ears listening / the amplitude / the wavelength / nothing) → the amplitudePrompt: Same note means same pitch. What makes it louder?
  2. In a skipping rope being shaken, 4 complete waves fit into 32 cm. What is the wavelength? → 8 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

eurekami

Measure and compare waves: amplitude and wavelength

Name

Date

Score/ 6

  1. Question 1

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

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

  2. Question 2

    In waves on a pond, 6 complete waves fit into 54 cm. What is the wavelength?

    Answercm

  3. Question 3

    Two water waves have amplitudes of 2 cm (wave A) and 6 cm (wave B). Which carries LESS energy?

    • A. wave A
    • B. wave B

  4. Question 4

    Wave A has crests 2 m apart. Wave B has crests 6 m apart. What can you say?

    • A. Wave B has a bigger amplitude.
    • B. Wave B has the longer wavelength.
    • C. Wave A has the longer wavelength.
    • D. They have the same wavelength.

  5. Question 5

    In waves on a pond, 3 complete waves fit into 9 cm. What is the wavelength?

    Answercm

  6. Question 6

    Two sound waves are drawn the same way. Wave A has an amplitude of 2 squares and wave B has 6 squares. Which is the LOUDER sound?

    • A. wave A
    • B. wave B

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Answer key: Measure and compare waves: amplitude and wavelength

  1. 1. D. The amplitude gets bigger, so the sound is louder.

  2. 2. 9 cm

  3. 3. A. wave A

  4. 4. B. Wave B has the longer wavelength.

  5. 5. 3 cm

  6. 6. B. wave B