Sound Cambridge IGCSE Co-ordinated Sciences (9–1) revision
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In plain words
Sound is a vibration passed on through particles, so it needs something to travel through: it can't cross a vacuum. Faster vibrations (a higher frequency) sound higher-pitched; bigger vibrations (a larger amplitude) sound louder. An echo is sound bouncing back.
Three things to know
- Sound is a longitudinal wave made by vibrations. It needs a medium and travels fastest in solids, slowest in gases (about 340 m/s in air).
- A higher frequency gives a higher pitch; a bigger amplitude gives a louder sound. Humans hear from about 20 Hz to 20 000 Hz; above that is ultrasound.
- An echo is a reflected sound. Distance to the reflector = speed × time ÷ 2.
Worked example
A shout echoes back from a cliff after 3 s. Sound travels at 340 m/s. How far away is the cliff?
- Total distance travelled = speed × time = 340 × 3 = 1020 m.
- That is there and back, so halve it.
- = 510 m.
Tips and tricks
- Echo questions: the sound goes there and back. Remember to divide by 2.
- Pitch goes with frequency, loudness goes with amplitude. Don't swap them.
It lands in your notebook with its questions as flashcards.
Sound: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What kind of wave is sound?
The particles vibrate along the direction the wave travels.
In which material does sound travel fastest?
Particles in a solid are closest together and pass vibrations on most quickly.
What is the approximate range of human hearing?
Sound above 20 000 Hz is ultrasound.
What does increasing the amplitude of a sound wave do?
Amplitude is linked to loudness, frequency to pitch.
An echo returns 2 s after a shout. Sound travels at 340 m/s. How far away is the cliff?
The sound travels 680 m in total, which is there and back.
What is ultrasound?
It is too high-pitched for humans to hear.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 10 marks. Write your answers on paper, then check them.
Sound
Cambridge IGCSE Co-ordinated Sciences (9–1) 0973 · 10 marks · papermunch.org
Name ______________________________ Date ______________
A girl claps and hears the echo from a wall 0.50 s later. Speed of sound = 340 m/s. Calculate the distance to the wall.[3]
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85 m. The sound travels 340 × 0.50 = 170 m, there and back.
Explain why sound cannot travel through a vacuum.[2]
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Sound is passed on by vibrating particles, and a vacuum has none.
State how the sound changes when (a) the amplitude and (b) the frequency of a sound wave increases.[2]
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(a) It becomes louder. (b) Its pitch becomes higher.
A ship sends an ultrasound pulse to the sea bed and receives the echo 0.40 s later. Speed of sound in water = 1500 m/s. Calculate the depth of the sea.[3]
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300 m. 1500 × 0.40 ÷ 2.
Answers: Sound
- 1. 85 m. The sound travels 340 × 0.50 = 170 m, there and back.
- 2. Sound is passed on by vibrating particles, and a vacuum has none.
- 3. (a) It becomes louder. (b) Its pitch becomes higher.
- 4. 300 m. 1500 × 0.40 ÷ 2.