Why can sound not travel through a vacuum?

There are no particles to vibrate and pass on the energy.

What is a compression?

A region of a sound wave where the particles are squashed close together (high pressure).

What is a rarefaction?

A region of a sound wave where the particles are spread further apart (low pressure).

What property of a sound wave decides its pitch?

Its frequency; a higher frequency gives a higher pitch.

What property of a sound wave decides its loudness?

Its amplitude; a larger amplitude gives a louder sound.

In which state of matter does sound travel fastest?

Solids, then liquids, then gases.

How do you find the distance to a wall from an echo?

Distance = speed × time ÷ 2, because the sound travels there and back.

Sound with a frequency above 20 kHz, higher than humans can hear.

Give two uses of ultrasound.

Scanning unborn babies, sonar, cleaning objects or testing for flaws in metal.

Sound wavesIB MYP Sciences: Flashcards

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How is sound produced?

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How is sound produced?: By vibrations.
Why can sound not travel through a vacuum?: There are no particles to vibrate and pass on the energy.
What type of wave is sound?: A longitudinal wave.
What is a compression?: A region of a sound wave where the particles are squashed close together (high pressure).
What is a rarefaction?: A region of a sound wave where the particles are spread further apart (low pressure).
What property of a sound wave decides its pitch?: Its frequency; a higher frequency gives a higher pitch.
What property of a sound wave decides its loudness?: Its amplitude; a larger amplitude gives a louder sound.
In which state of matter does sound travel fastest?: Solids, then liquids, then gases.
What is the speed of sound in air?: About 340 m/s.
How do you find the distance to a wall from an echo?: Distance = speed × time ÷ 2, because the sound travels there and back.
What is the range of human hearing?: About 20 Hz to 20 kHz.
What is ultrasound?: Sound with a frequency above 20 kHz, higher than humans can hear.
Give two uses of ultrasound.: Scanning unborn babies, sonar, cleaning objects or testing for flaws in metal.

Exam questions on Sound waves

Astronauts on a spacewalk outside a space station cannot hear each other speak, even when they are only one metre apart, so they talk by radio. Inside the station, where there is air, the same astronauts can talk normally.
Describe what is meant by a compression and by a rarefaction in a sound wave.2 marks
A hiker in a valley in Switzerland shouts towards a large cliff and hears her echo 0.80 s later. The speed of sound in air is 340 m/s.
The hiker walks to a new position, shouts again and hears the echo 1.2 s later. Calculate her new distance from the cliff.2 marks
Students in Cairo measure the speed of sound in air. They stand 100 m from a large flat wall and clap their hands. A partner uses a stopwatch to time the delay between the clap and the echo. Five repeat readings are 0.66 s, 0.54 s, 0.62 s, 0.55 s and 0.58 s. The students know that the accepted speed of sound in air is about 340 m/s.
Calculate the mean time and use it to find the speed of sound in air from the students' results.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).