中文（繁體）
中文（简体）
English
S3 Physics: Sound Waves, Frequency, Speed and Echo (Paper 4: mistake clinic)
S3 Physics: Sound Waves, Frequency, Speed and Echo (Paper 4: mistake clinic)
This last paper revisits three frequent errors: halving forgotten in echoes, frequency taken for loudness and the belief that a vacuum carries sound faster.
Direct answers Spend three seconds checking those three points after every question, which works better than rereading the notes.
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)
- FoundationHow are speed, frequency and wavelength related?
- FoundationWhy is there no sound at all in a vacuum?
- FoundationWhat decides pitch?
- IntermediateAt 340 m/s with a wavelength of 0.25 m, what is the frequency?
- IntermediateWhat is the wavelength of 34 kHz ultrasound in air at 340 m/s?
- IntermediateA target is 170 m away at 340 m/s. How long until the echo returns?
- ChallengeA bat gets an echo 0.02 s after its cry at 340 m/s. How far is the prey?
- ChallengeShouting into a well 68 m deep at 340 m/s, when is the echo heard?
- ChallengeWhen the same frequency passes from air into water, how does the wavelength change?
- Error redoA student says a higher frequency always means a louder sound. Where is the error?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | v = f lambda, speed equals frequency times wavelength | Any two of the three give the third, with units of m/s, hertz and metres. |
| 2 | There are no particles to pass the vibration on | Sound is a mechanical wave that needs particles to hand the vibration along, and a vacuum has none. |
| 3 | Frequency, with a higher frequency giving a higher pitch | Loudness comes from amplitude, and the two must not be mixed up. |
| 4 | 1,360 Hz, which is 340 divided by 0.25 | Using f = v over lambda gives 1,360 Hz, still inside the audible range. |
| 5 | 0.01 m, which is 1 cm | Dividing 340 by 34,000 gives 0.01 m, and ultrasound wavelengths are usually quoted in millimetres. |
| 6 | 1.0 s | The two-way path is 340 m, which at 340 m/s takes one second. |
| 7 | 3.4 m | Taking 340 times 0.02 and halving gives 3.4 m, the short-range precision of echolocation. |
| 8 | 0.4 s | The round trip is 136 m and dividing by 340 gives 0.4 s. |
| 9 | It lengthens to about 4.41 times the value in air, from 1,500 over 340 | The frequency stays fixed so the wavelength grows in the same proportion as the speed. |
| 10 | Frequency sets pitch while amplitude sets loudness, so the two are independent | A faint high note and a booming bass drum show the two properties move independently. |
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.
Keep three columns in the error log: question, cause, corrected steps. The three commonest slips are forgetting the factor of two, treating frequency as loudness, and believing sound travels faster in a vacuum.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.