The shape of the lesson
By the end of the lesson, learners can
- Read a wave off the screen: Change the amplitude and frequency and watch the wavelength and period respond.
- Four numbers describe any wave: Wavelength, amplitude, frequency and period are linked, and frequency is simply one over the period.
One picture every idea returns to
A wave transfers energy without transferring matter. Its wavelength is the distance for one complete wave, its amplitude is the maximum displacement from rest, its frequency is the number of waves per second in hertz, and its period is the time for one wave.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, The anatomy of a wave.. Drop a stone in a pond and rings race outward, yet a floating leaf only bobs in place. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Read a wave off the screen | Change the amplitude and frequency and watch the wavelength and period respond. Project tab 1 of the lab (Wave features) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Four numbers describe any wave | Wavelength, amplitude, frequency and period are linked, and frequency is simply one over the period. Model the worked example Worked example on the board, one line at a time. | Connect-Extend-Challenge |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (5 questions, 18 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Four numbers describe any wave, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Connect-Extend-Challenge
After the new idea, each student writes three lines: how it connects to what they knew, how it extends their thinking, and what still challenges them. Pairs compare, then the challenges become the plenary.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| A wave transfers energy, not matter: the water, air or rope it travels through stays put on average. | And amplitude is measured from the rest position to a crest, not all the way from a crest down to a trough. |
Wave features (wavelength, amplitude, frequency): worksheet
5 questions, 18 marks. Written in the style of the papers; no past paper question is reproduced.
State the SI unit, including its symbol, for each of the following wave quantities.
(a) wavelength (b) frequency (c) amplitude (d) periodA sound wave produced by a tuning fork has a frequency of 250 Hz. Calculate the period of the wave.
A wave on a stretched rope oscillates between a peak that is 7 cm above the rest position and a trough that is 7 cm below it. A student claims the amplitude of the wave is 14 cm.
Explain why the student is incorrect and state the correct value of the amplitude.
Two sound waves, A and B, are produced by different sources and displayed on the same displacement-time graph.
Wave A completes 8 oscillations in 2.0 seconds, and has an amplitude of 0.04 m.
Wave B completes 4 oscillations in 2.0 seconds, and has an amplitude of 0.08 m.
(a) Calculate the frequency of each wave. [2] (b) Calculate the period of each wave. [2] (c) Describe how the two sounds would differ to a listener. [1]A small buoy floats on the surface of the sea. As waves pass, the buoy bobs up and down. A student observing the buoy from a nearby pier notes the following:
• In 30 seconds, the buoy completes 15 full up-and-down oscillations.
• At the highest point of each wave, the buoy is 0.60 m above its rest position.
Answer key and marking notes
(a) wavelength → metres (m) ✓
(b) frequency → hertz (Hz) ✓
(c) amplitude → metres (m) ✓
(d) period → seconds (s) ✓
Each correct unit with its symbol is worth 1 mark. Don't lose marks by writing "Hertz" without the symbol Hz.
Use: T = 1 ÷ f
T = 1 ÷ 250 T = 0.004 sT = 4 × 10⁻³ s
Either 0.004 s or 4 ms gets the full mark. Always include the unit.
Why the student is wrong:
Amplitude = max displacement from rest position to the peak (or trough).
The student has measured peak-to-trough distance, which is twice the amplitude.
Correct value:
amplitude = 7 cm
Common mistake. Always measure amplitude from rest, never crest to trough.
(a) Frequencies
Wave A: f = 8 ÷ 2.0 = 4 Hz Wave B: f = 4 ÷ 2.0 = 2 Hz(b) Periods
Wave A: T = 1 ÷ 4 = 0.25 s Wave B: T = 1 ÷ 2 = 0.50 s(c) Comparison of sound
Wave A: higher pitch, quieter
Wave B: lower pitch, louder
Higher frequency → higher pitch. Larger amplitude → louder. Two independent properties.
(a) Frequency
f = oscillations ÷ time f = 15 ÷ 30 = 0.5 Hz(b) Period
T = 1 ÷ f = 1 ÷ 0.5T = 2.0 s
(c) Amplitude
a = 0.60 m
Amplitude here is given directly as the height above rest. No calculation needed.
3 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
What is meant by the amplitude of a wave?
- AThe maximum displacement of a point from its rest position.
- BThe distance between two adjacent crests.
- CThe number of complete waves passing a point each second.
- DThe time taken for one complete wave to pass.
The diagram shows a transverse wave. Which labelled distance is one wavelength?
- AP
- BQ
- CR
- Dnone of these
A wave has a frequency of 4.0 Hz. What is its period?
- A0.25 s
- B0.40 s
- C4.0 s
- D8.0 s
Quiz key
Amplitude is the greatest displacement from the undisturbed (rest) position. Option B is the wavelength, C is the frequency, and D is the period.
P spans one full cycle (crest to crest), which is the wavelength. Q is the amplitude (rest to crest), and R is the crest-to-trough distance, which equals twice the amplitude.
T = 1 ÷ f = 1 ÷ 4.0 = 0.25 s. Option C uses the frequency value as if it were the period.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.