中文（繁體）
中文（简体）
English
S4 Physics Waves Practice Paper 3 | v = f x lambda in Three Directions, Deep and Shallow Water Wavelengths: 10 Questions with Answers
S4 Physics Waves Practice Paper 3 | v = f x lambda in Three Directions, Deep and Shallow Water Wavelengths: 10 Questions with Answers
The third set of ten wave questions, practising v = f x lambda in all three directions, period, wavelength changes between deep and shallow water, ultrasound depth sounding and echo ranging, each with an answer and a one-line explanation.
Direct answers This paper has 10 questions, from the wave speed formula to ultrasound and echoes, taking the speed of sound as 340 m/s and the speed in water as 1 500 m/s; about 25 minutes is suggested.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 3 · Intermediate 4 · Challenge 2 · Error redo 1 |
| Chapter | S4 Physics: Waves |
| Level | S4 (DSE) |
02 Questions (10 items)
- FoundationA wave has a frequency of 400 Hz and a wavelength of 0.85 m. What is its speed?
- FoundationWhat is the period of a wave of frequency 20 Hz?
- FoundationA shout towards a cliff produces an echo 0.8 s later. How far away is the cliff? (speed of sound 340 m/s)
- IntermediateThe speed of sound in water is 1 500 m/s and the frequency is 500 Hz. What is the wavelength?
- IntermediateA wave of frequency 5 Hz has a wavelength of 4 m. Find its speed and its period.
- IntermediateA wave travels at 8 m/s in deep water with a frequency of 4 Hz, then enters shallow water where its speed is 4 m/s. Find the wavelength in deep water and in shallow water.
- IntermediateThunder is heard 4 s after the lightning is seen. How far away did the lightning strike? (speed of sound 340 m/s)
- ChallengeA ship sends ultrasound from its hull and receives the echo after 0.05 s. How deep is the seabed? (speed of sound in water 1 500 m/s)
- ChallengeA wave travels at a constant 300 m/s. If its frequency rises from 100 Hz to 300 Hz, what does the wavelength change from and to?
- Error redoA shout towards a cliff is heard as an echo 2 s later. How far away is the cliff? (speed of sound 340 m/s; a common wrong answer is 680 m)
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | v = f x lambda = 400 x 0.85 = 340 m/s. | Wave speed is frequency times wavelength, and the units must be consistent. |
| 2 | T = 1 / f = 1 / 20 = 0.05 s. | Frequency and period are reciprocals. |
| 3 | s = 340 x 0.8 / 2 = 136 m. | The echo travels there and back, so it must be divided by 2. |
| 4 | lambda = v / f = 1 500 / 500 = 3 m. | With the speed and the frequency given, divide directly to get the wavelength. |
| 5 | v = 5 x 4 = 20 m/s; T = 1 / 5 = 0.2 s. | The two relationships are used together: v = f x lambda and T = 1 / f. |
| 6 | In deep water, lambda = 8 / 4 = 2 m; in shallow water, lambda = 4 / 4 = 1 m. | The frequency is set by the source and does not change, so half the speed gives half the wavelength. |
| 7 | s = 340 x 4 = 1 360 m. | Light travels so fast that the time gap is essentially the time the sound takes. |
| 8 | s = 1 500 x 0.05 / 2 = 37.5 m. | The pulse also travels there and back, so the time must be divided by 2. |
| 9 | Before, lambda = 300 / 100 = 3 m; after, lambda = 300 / 300 = 1 m. | In the same medium the speed is unchanged, so tripling the frequency cuts the wavelength to one third. |
| 10 | s = 340 x 2 / 2 = 340 m. | Forgetting to divide by 2 gives twice the true distance. |
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.
Work through all ten questions under timed conditions first, then check each answer against its one-line explanation and redo the ones you got wrong.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.
