中文（繁體）
中文（简体）
English
S4 Physics Waves Practice Paper 4 | Constant Speed in a Medium, Frequency Set by the Source and Echo Ranging: 10 Questions with Answers
S4 Physics Waves Practice Paper 4 | Constant Speed in a Medium, Frequency Set by the Source and Echo Ranging: 10 Questions with Answers
The fourth set of ten wave questions, practising v = f x lambda in all three directions, frequency and period, echo and ultrasound ranging, wavelength changes between deep and shallow water and a comparison of wavelengths in air and water, each with an answer and a one-line explanation.
Direct answers This paper has 10 questions, from the wave speed formula to echoes and refraction, 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 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | S4 Physics: Waves |
| Level | S4 (DSE) |
02 Questions (10 items)
- FoundationA wave has a frequency of 250 Hz and a wavelength of 1.2 m. What is its speed?
- FoundationThe speed of sound is 340 m/s and the frequency is 680 Hz. What is the wavelength?
- FoundationThe period of a wave is 0.02 s. What is its frequency?
- Foundation20 waves pass a point in 4 s. What are the frequency and the period?
- IntermediateA shout towards a cliff is heard as an echo 3.4 s later. How far away is the cliff? (speed of sound 340 m/s)
- IntermediateA sonar sends out ultrasound and receives the echo after 0.02 s. How far away is the target? (speed of sound in water 1 500 m/s)
- IntermediateA wave travels at 6 m/s in deep water with a frequency of 3 Hz, then enters shallow water where its speed is 3 m/s. Find the wavelength in deep water and in shallow water.
- ChallengeWhat are the wavelengths of a 500 Hz sound in air at 340 m/s and in water at 1 500 m/s?
- ChallengeWave A has a frequency of 200 Hz and a wavelength of 1.5 m. Wave B, in the same medium, has a frequency of 300 Hz. Find the wavelength of wave B.
- Error redoA sound wave has a frequency of 500 Hz and a wavelength of 0.68 m. What is its speed? (a common wrong answer is 735 m/s)
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | v = f x lambda = 250 x 1.2 = 300 m/s. | Wave speed = frequency x wavelength. |
| 2 | lambda = v / f = 340 / 680 = 0.5 m. | With the speed and the frequency given, divide directly. |
| 3 | f = 1 / T = 1 / 0.02 = 50 Hz. | Frequency and period are reciprocals. |
| 4 | f = 20 / 4 = 5 Hz; T = 1 / 5 = 0.2 s. | Divide the number of waves by the time to get the frequency, then take the reciprocal for the period. |
| 5 | s = 340 x 3.4 / 2 = 578 m. | The echo travels there and back, so the time must be divided by 2. |
| 6 | s = 1 500 x 0.02 / 2 = 15 m. | Underwater ultrasound also travels there and back, so the distance one way only comes after dividing by 2. |
| 7 | In deep water, lambda = 6 / 3 = 2 m; in shallow water, lambda = 3 / 3 = 1 m. | The frequency is set by the source and does not change, so halving the speed halves the wavelength. |
| 8 | In air, lambda = 340 / 500 = 0.68 m; in water, lambda = 1 500 / 500 = 3 m. | The frequency is unchanged, so a greater speed gives a longer wavelength. |
| 9 | The speed is v = 200 x 1.5 = 300 m/s, so the wavelength of wave B is 300 / 300 = 1 m. | The speed is the same in the same medium, so find the speed from wave A first and then the wavelength of wave B. |
| 10 | v = 500 x 0.68 = 340 m/s. | Wave speed is frequency times wavelength; dividing the wavelength by the frequency gives an absurdly high speed. |
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.
