What is it?

the __________ of the pulse E. The Doppler Effect A bug jumps once on a pond, creating a pulse. (top view) bug _____________ :  all points drawn are the __________ of the pulse all points have ___________________________ the shape is __________________ wavefront peak the same phase a circle

l l A bug jumps at a ___________, constant f creating waves. side view newest wavefront A bug jumps at a ___________, creating waves. v constant f l bug side view of waves l oldest wavefront What would a diagram of the troughs look like? perpendicular The wave v's are ______________________ to the wavefronts.

spheres In 3-dimensions, the wavefronts are _________________.

Far away from the wave source, the wavefronts become _________________ and more like _________________. less spherical plane waves wavefronts = surfaces with ____________________ wave source equal phase spherical waves nearly plane waves Far away, the wave velocity vectors become ____________ parallel

Now bug moves left while jumping at a constant frequency l shorter l higher 4 3 2 1 _________ l _________ f longer lower old wavefront is __________________ newer wavefront _________________ centered on 1 centered on 2

It doesn't matter whether the source is moving… observer: Observer measures: wave source: v _________ l _________ f shorter v =0 higher v _________ l _________ f longer v =0 lower …or if the observer is moving with the source at rest: Observer measures: v =0 v _________ l _________ f shorter higher v =0 v _________ l _________ f longer lower

The Doppler Effect – a shift in the ____________________ of a wave caused by _________________________between a ____________ and __________________. observed frequency relative motion source an observer 1. Is true ______________________________ waves. for sound, light, water, etc. 2. The __________ f of the source ______________________ . actual does NOT change 3. The f is ____________ and the l is ___________ if the distance between observer and source is ____________ and ______________________ . higher shorter decreasing vice versa The speed of the wave itself is _____________________ ________________________ . the same on both sides of the source

5. If a sound source is approaching you, you will hear a sound with a __________________________ . If it is receding from you, you will hear a sound that is _________________ . higher pitch lower in pitch 6. __________ light has a shorter l than ________ light. Light sources that are approaching an observer will have ____________ l and _____________ f . This is called a __________ shift. Light sources that are receding from an observer will have ____________ l and _____________ f. This is called a __________ shift. Blue red shorter higher blue longer lower red 7. The faster the speed of the source or the observer, the _______the shift in l and f. more

Applications of the Doppler Effect: 1. radar: return time  ______________________ Doppler radar  ______________________  ______________________ 2. measure ____________________________ speeds 3. monitor _________________________ 4. aid in diagnosis of ____________________________ 5. red shift/blue shift of _____________________ 6. measuring rotation of _______________________ 7. ______________________________________________ distance to storm speed of storm approaching or receding car or baseball blood flow deep-vein thrombosis galaxies the Sun or a galaxy motion detectors—security systems

receding from Earth  red shifted approaching Earth  blue shifted

at rest with respect to Earth red shifted  galaxy is moving away (receding)

Using the Doppler Effect, Hubble found that the farther a galaxy was, the faster it was moving. A modern Hubble Diagram:

Stationary Sound Source

Source moving with vsource < vsound ( Mach 0.7 )

Source moving with vsource = vsound ( Mach 1 - breaking the sound barrier )

Source moving with vsource > vsound (Mach 1.4 - supersonic)

Sonic booms – occur when _____________________ exceeds the ________________________ in the medium. The wavefronts _______________ in a _________________ that is dragged behind the ________________________ . The wavefronts _____________________ to produce a large ________________________________________. The same thing happens when a ____________ travels faster than the speed of _____________________ and leaves behind a _______________________ . speed of a source speed of waves pile up cone shape wave source add together amplitude shock wave boat water waves large wake