Goodbye

May is a time of goodbyes. Last night was my final quartet concert with Kellie, Steph, and Mirabel (aka the best quartet ever) :(. We have been together for three years, so I am very sad that they are all graduating. We played a Shostachovich quartet that was, well, different. My mom thought it was weird, and I think my dad thought so too. It was definitely a piece of music that was outside the box for all of us, but we all enjoyed playing it. It was also pretty short because Mr. Stark got in trouble last semester since our piece was so long. This is a brief video of our rehearsal before my camera died. After the concert, Kellie drove us to yogurtland, and we had a nice time eating yogurt and talking :)

Tomorrow is the physics exam! So I shouldn't really have to explain the physics in this video since we should all know it already :) Sound waves, frequency, wavelength, all that good stuff. This year really has flown by. I remember the first day of physics clearly, as we all sat innocently in our seats, not yet enlightened on the wonders of physics or aware of the stress that lay ahead. For me, this was the hardest class I have ever taken, but I do not regret taking it. On the contrary, it has been a great learning experience. So goodbye, physics blogs and good luck to everyone tomorrow!

MRI

One of my friends had to get an MRI this past weekend, and I didn't really understand what an MRI was, so I googled it. As it turns out, MRI scans have a lot to do with physics, particularly magnetism. First of all, I learned that MRI stands for magnetic resonance imaging. MRI machines use magnets and radio waves to create a picture of the inner human body.

The magnets used in MRI machines produce a magnetic field between 0.5 and 2 teslas. There are many different types of atoms in the human body, but MRI machines focus on hydrogen atoms. Hydrogen atoms have a large magnetic moment, so when they are placed in a magnetic field, they line up with the direction of the magnetic field.

All of the hydrogen protons will align with the magnetic field in one direction or the other. The vast majority cancel each other out, but, as shown here, in any sample there is one or two "extra" protons.

These extra protons are what create the images. The MRI machines applies a radio wave frequency that is specific to hydrogen, and these radio waves are directed at the part of the body that is being examined. The atoms in this region of the body then absorb the energy from the radio waves, and this causes them to spin in a different direction. Then when the radio wave frequency is turned off, the hydrogen atoms return to their natural alignment and release their excess stored energy. This release of excess energy is essentially what creates the final image that can help doctors diagnose injuries and other health problems.

(information from http://health.howstuffworks.com/mri7.htm)