Sound Waves
Class 9 Science: sound (frequency, wavelength and speed)
Change the frequency and the material sound travels through. Watch the compressions and see speed = frequency × wavelength.
Words to know
- Compression
- A region where the particles are pushed close together.
- Rarefaction
- A region where the particles are spread apart.
- Frequency
- Vibrations per second, measured in hertz (Hz).
- Wavelength
- The distance from one compression to the next.
- Speed of sound
- About 340 m/s in air, faster in water and fastest in solids.
Quick check
Answer 3 questions to check what you learned.
Try at home
Put your ear on a table and ask a friend to tap the far end softly. Then listen with your head up. Through which is the tap louder?