PHYS - Sound Waves
Physics, waves, sound waves - IBDP | DSE | GCE | IAL | AP Physics
Are sound waves longitudinal waves or transverse waves?
Sound waves are longitudinal waves. It means the particles vibrate parallel to the direction of travel.
Speed of Sound Waves
Speed of sound in different medium: solid > liquid > gas
Speed travels fastest in solid because the particles to carry the vibrations are close to each other in solids while they are far away in gases.
The speed of sound in air is approximately 340 m/s.
IGCSE Physics may ask how you can obtain the speed of sound experimentally 👉
- Using data logger and two microphones: The data logger can record the time it takes for sound to reach two microphones. The speed of sound then can be determined by dividing the distance between two microphones by the time.
- Clap-echo method: Stand a certain distance apart from the wall. Make a sharp clap and measure the time for an echo to be heard. The speed of sound then can be determined by dividing two of the distance between you and the wall by the time you measured.
Properties of Sound Waves
- The pitch of sound is relevant to frequency of sound wave.
- The loudness of sound is relevant to amplitude of sound wave.
It is expected in IGCSE Physics that you understand how to calculate the frequency of sound using an oscilloscope
We can visualize sound waves by using an oscilloscope 👩💻 If we connect a microphone to an oscilloscope, the oscilloscope will display the sound wave transmitted to the microphone.
Two ways to obtain frequency:
- Find out how many cycles of wave are completed in one second.
- Find out the time that it takes for one cycle of wave to be completed. Then find the inverse of the time.
- There are three cycles of waves during 1 second, so the frequency is 3 Hz.
- It takes 1/3 second for one cycle to be completed, so the frequency is 1/(1/3) = 3 Hz.
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