The Doppler EffectApparent change in frequency of a sound

relative to the object’s motion.As the source moves closer, observed frequency

increases.As the source moves away, observed frequency

decreases.Can occur when

Source is moving relative to a stationary observer

Observer is moving relative to a stationary source

Stationary Source & Observer

Moving Source

http://www.fisica.uniud.it/~deangeli/applets/Multimedia/Waves_java/Doppler/doppler.htm

Example 1You are standing at a railway crossing. A train approaching at 125 km/h sounds its whistle. If the frequency of the whistle is 442 Hz and the air temperature is 20.0°C, what frequency do you hear when the train approaches you? When the train has passed you?

Supersonic TravelSubsonic speed: less than the speed of sound

in air

Mach number: Mach = speed of object speed of sound

Supersonic speed: when Mach > 1

http://www.fisica.uniud.it/~deangeli/applets/Multimedia/Waves_java/Doppler/doppler.htm

Sound barrier: high pressure region produced when plane approaches Mach 1

A shock wave is produced when the place “breaks” through this barrier.

Sonic boom Explosive sound that radiates from aircraft

travelling at supersonic speedsCaused by constructive interference of spheres

of sound waves that are left behind the aircraft

The space shuttle, on re-entry:http://www.youtube.com/watch?v=lNL4HHFG8H4http://www.youtube.com/watch?v=Oo_1HeravCY&feature=relatedhttp://www.youtube.com/watch?v=a1CU6VVE0AA&feature=related

If time, Mythbusters:http://www.youtube.com/watch?v=GvtAElaDVz8

Homework9.5 Practise #1, 2 pg 4359.5 Questions #2-6 pg 435