The shape of the lesson
By the end of the lesson, learners can
- Match the trace: Adjust amplitude and frequency to match a target wave, and watch how each control changes a different feature.
- Two dials, two effects: Amplitude and frequency act independently, so changing one does not change the other.
- Amplitude controls loudness: taller wave, louder sound.
- Frequency controls pitch: more waves in the same time, higher pitch.
- On a CRO: height shows loudness, the number of waves across the screen shows pitch.
One picture every idea returns to
The loudness of a sound depends on the amplitude of the wave: a larger amplitude is louder. The pitch depends on the frequency: a higher frequency is a higher pitch. The two are independent, so a sound can be loud and low, or quiet and high.
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, Taller, or tighter.. Turn up the volume and the trace on an oscilloscope grows taller. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Match the trace | Adjust amplitude and frequency to match a target wave, and watch how each control changes a different feature. Project tab 3 of the lab (Loudness and pitch) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Two dials, two effects | Amplitude and frequency act independently, so changing one does not change the other. | Anticipation / Reaction Guide |
| 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 (6 questions, 13 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 Two dials, two effects, 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.
Anticipation / Reaction Guide
Before the lesson, students mark five statements true or false. After the teaching they mark them again and justify any change of mind in one sentence each. The statements come from the examiner traps below.
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 |
|---|---|
| Amplitude controls loudness and frequency controls pitch, and they are independent. | Turning up the volume makes the trace taller, it does not pack the waves closer. Packing more waves into the same width raises the pitch, it does not make the sound louder. |
Loudness and pitch: worksheet
6 questions, 13 marks. Written in the style of the papers; no past paper question is reproduced.
State which property of a sound wave determines:
(a) the loudness of the sound, [1] (b) the pitch of the sound. [1]Define the amplitude and the frequency of a wave.
A sound is displayed on an oscilloscope. The same note is then played more loudly. Describe how the trace changes, and how it stays the same.
On the same oscilloscope, a higher-pitched note is now played at the same loudness as before. Describe how this trace differs from the first.
A student writes that increasing the amplitude of a sound makes it higher pitched. Explain what is wrong with this statement.
Two sounds, P and Q, are displayed on the same oscilloscope with identical settings.
Answer key and marking notes
(a) The amplitude. ✓
(b) The frequency. ✓
- Amplitude is the maximum displacement of a point from its rest (undisturbed) position. ✓
- Frequency is the number of complete vibrations (or waves) per second, measured in hertz. ✓
- The trace becomes taller, because the amplitude is larger. ✓
- The number of waves across the screen stays the same, because the frequency (pitch) is unchanged. ✓
- More waves fit across the same width of screen, because the frequency is higher. ✓
- The height of the trace is the same, because the loudness (amplitude) is unchanged. ✓
- Increasing the amplitude makes the sound louder, not higher pitched. ✓
- Pitch is changed by the frequency, not the amplitude. ✓
(a) Q is louder. ✓ Its trace has a larger amplitude (it is taller). ✓
(b) They have the same pitch, because they show the same number of waves across the screen (same frequency). ✓
Q is taller but has the same number of waves, so it is louder at the same pitch.
2 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.
On an oscilloscope, how is a louder sound shown compared with a quieter one of the same pitch?
- Awith a larger amplitude
- Bwith a higher frequency
- Cwith more waves on the screen
- Dwith a shorter wavelength
A sound of higher pitch is shown on an oscilloscope by a wave with:
- Aa higher frequency, so the waves are closer together
- Ba larger amplitude
- Ca taller trace
- Da flatter line
Quiz key
A louder sound has a larger amplitude, so the trace is taller. The number of waves (frequency) sets the pitch, not the loudness, so options B and C describe pitch instead.
Higher pitch means higher frequency, so more waves fit on the screen and they appear closer together. Amplitude (B, C) controls loudness, not pitch.
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.