Year+13+Doppler+Effect


 * __The Doppler Effect:__ **

We hear this effect most days, without even realising it. When a car drives past you you hear it's the pitch of it's engine change, you can hear, and recognise, how fast it is going without seeing it. The faster a car is going, the higher it's pitch is when it is approaching you.





The Doppler effect has shaped our ideas about how the universe has formed, understanding how this

principle showed us that the universe is expanding, and so the "Big Bang" theory has been widely accepted as a starting point for delving into the beginnings of the universe.



Here are some applets to help you with understanding how the wave fronts get "bunched up":
 * This one lets you play with all sorts of different scenarios.
 * This one lets you "hear" the wave as "clicks".
 * This is a good website with a few videos and lots of explanations.
 * Very cute poster website.


 * The Sonic Boom: **

When an object passes through the air, it creates a series of pressure waves in front of it and behind it, similar to the waves created by a boat. These waves travel at the speed of sound (approximately 343 m/s), and as the speed of the object increases, the waves are forced together, or compressed, because they cannot "get out of the way" of each other, eventually merging into a single shock wave at the speed of sound. This critical speed is known as Mach 1 and is approximately 1,225 km/h (which is approximately the speed of sound in km/h).



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Great Video, watch it!