Beats, Doppler Shift, and Shock Waves

Today was fun.  We started out with a discussion of beat frequencies.  The class video will be posted soon.

You can play around with beat frequencies at the following Beat Frequency Physlet.  Although Beat frequencies are most relevant to music, we will return to beats when we get to optics and modern physics!  Last week was exciting because I got my piano tuned and Alejandro got to see someone who gets paid to listen to beat frequencies!

The effects of Doppler Shifts are cool.  Again, David Latham talked about this at ASM.  Except instead of the Doppler Shift in acoustic waves, he uses the Doppler Shift of light (blue shift/red shift) to measure the wobble in stars around the center of mass of a stat-planet system.  You can read about David Latham’s project at the AFOE homepage. If you want to play with a Doppler Shift physlet. What is cool about this physlet is you can adjust the speed to greater than the wave speed to create shock waves!

As I mentioned in class, I was watching NOVA last week with Alejandro.  The episode of NOVA was on Japan and the Earthquake. There was so much relevant to out current class discussion.  The triangulation of Earthquakes using S and P waves.  The refraction or change in water wave speed which causes Tsunamis.  But relevant to today’s discussion of shock waves was that they showed footage of the Cherenkov radiation being emitted from a nuclear reactor.  The Cherenkov radiation is essentially an optical shock wave, when electrons are moving faster than the speed of light in water.  A reactor has an strange blue glow. I got to see this was I was a young physics teacher and spent two weeks in a summer program at the Nuclear Reactor at Penn State.