A common misconception by students is to associate sound waves produced by a sound system with radio waves. Signal is transmitted in the air via radio waves from the radio stations in the form of transverse waves. When sound which you hear that is produced from the speaker is sound waves which are longitudinal waves.
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When you break the sound barrier (speed of sound is approximately 330 m/s), a sonic boom is created. Take a look at this great video clip on sonic boom. Enjoy =)
Recall speed of light is 3 x 108 m/s. Hence during stormy days, you see the lightning first before you hear the thunder 😉
SR-71 Blackbird is the fastest aircraft in the world, though it is no longer in service. It is the the first aircraft to break the sound barrier.
A man who is standing at a point X between two parallel walls (as shown in the diagram) fires a starting pistol.
He hears the first echo after 0.6s and another one after 0.8s. How long after firing the pistol will he hear the next echo?
View video tutorial to visualise the distance travelled.
Time taken to hear next echo = 0.6 + 0.8 = 1.4s
The distance travelled by sound (left and right) from X is the same during 3rd and 4th echos.
Hence 3rd and 4th echos actually coincide. And time taken is 0.6 + 0.8 = 1.4s.