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S3 Physics: Sound Waves, Frequency, Speed and Echo (Paper 2: intermediate)
S3 Physics: Sound Waves, Frequency, Speed and Echo (Paper 2: intermediate)
This second paper adds units and a comparison of media, then puts echo ranging into the real settings of sonar and thunder.
Direct answers Write the knowns, the unknown and the formula before substituting, which removes most slips.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S3 Physics: Sound Waves, Frequency, Speed and Echo |
| Level | S3 Physics |
02 Questions (10 items)
- FoundationIn which state does sound usually travel fastest?
- FoundationWhat is the approximate audible frequency range for humans?
- FoundationWhat is the period of a 250 Hz sound wave?
- IntermediateA sonar pulse returns after 4 s in water where sound travels at 1,500 m/s. How far is the target?
- IntermediateAt 20,000 Hz and 340 m/s, what is the wavelength?
- IntermediateAn ultrasonic cleaner runs at 40 kHz in air at 340 m/s. What is the wavelength?
- ChallengeThunder arrives 5 s after the lightning flash at 340 m/s. How far away did it strike?
- ChallengeIf the wavelength doubles in the same medium, what happens to the frequency?
- ChallengeA shout in a valley returns after 3 s at 340 m/s. How far is the cliff?
- Error redoA student works out that a wall is 204 m away from a 0.6 s echo at 340 m/s. Where is the error?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Fastest in solids, then liquids, slowest in gases | Particles are packed closest in a solid so the vibration passes on fastest, reaching about 5,000 m/s in steel. |
| 2 | About 20 Hz to 20,000 Hz | Below 20 Hz is infrasound and above 20,000 Hz is ultrasound, and neither is heard by the human ear. |
| 3 | 0.004 s | Period is the reciprocal of frequency, so 1 divided by 250 gives 4 milliseconds per vibration. |
| 4 | 3,000 m, which is 1,500 times 4 divided by 2 | The pulse covers 6,000 m in total so the target sits at half of that. |
| 5 | 0.017 m, which is 17 mm | Dividing 340 by 20,000 gives 0.017 m, the wavelength at the top of the audible range. |
| 6 | 0.0085 m, which is 8.5 mm | Dividing 340 by 40,000 gives 0.0085 m, and higher frequency means shorter wavelength and more concentrated energy. |
| 7 | 1,700 m, which is 340 times 5 | Light arrives almost instantly so the sound covers a single trip and no halving is needed. |
| 8 | It halves | With speed fixed, v = f lambda makes wavelength and frequency inversely related. |
| 9 | 510 m, which is 340 times 3 divided by 2 | The round trip covers 1,020 m so one way is 510 m. |
| 10 | The factor of two is missing: 204 m is the round trip so the wall is 102 m away | An echo completes the journey out and back while the distance asked for is one way only. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
The intermediate paper is about rearranging: the same v = f lambda serves three ways, and every echo question needs the there-and-back path, so distance is speed times time divided by two.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.