Science Class 9
Sound Waves: Characteristics and Applications
How sound is made, how it travels, its wavelength, and how echoes measure distance.
13 lessons · ~72 min total
Track progress — 0 of 13 lessons read 0%
Lessons in this topic
- 0 Start here What this chapter is about, in one picture. · 3 min You are here
- 1 Something has to shake Every sound is made by something that shakes. Stop the shaking and the sound stops. · 5 min
- 2 It needs something to travel through Sound needs a medium. It usually travels fastest in solids, and not at all in a vacuum. · 6 min
- 3 What actually moves A sound wave travels through the medium. The pieces of the medium only shake in place. · 6 min
- 4 How loud it is A bigger amplitude means a louder sound. Loudness does not change the speed. · 6 min
- 5 How often it shakes Frequency counts shakes in one second. A higher frequency is a higher pitch. · 6 min
- 6 What we can hear People hear 20 Hz to 20 000 Hz. Below that is infrasound. Above that is ultrasound. · 5 min
- 7 Checkpoint: loudness, pitch and hearing A graded check on loudness, frequency and the range we hear. · 5 min
- 8 It comes back A hard surface reflects sound. A gap of 0.1 s or more is heard as an echo. · 6 min
- 9 Putting the return to work Sonar times an echo to find a distance under water. The distance is half the trip. · 6 min
- 10 Wavelength, frequency and speed Speed = wavelength × frequency. At one speed, a higher frequency gives a shorter wavelength. · 8 min
- 11 The big picture Nine ideas about sound, on one screen. · 4 min
- 12 Track quiz The nine rules, then one question on each idea. · 6 min
0%
Take this year's practice exam →
Draws questions from every track in this subject's year, not just this one — a Practice result, never official.