Hot wings carryout from the cafeteria. It is not advisable to eat and use the keyboard in a parallel fashion.
That is all.
Daily Archives: February 13, 2009
Follow the Bouncing Atom
Bouncing atoms take a measure of gravity
Pretty cool. The experiment uses a technique used in interferometry, where a laser standing wave induces an absorption-emission cycle of an atom, so it receives a momentum “kick” of twice the photon momentum (one kick for absorption, and once for emission), effectively making a diffraction grating out of light if they were moving through the standing wave, and uses this to bounce the falling atoms.
If the colour of the laser light and the frequency of pulses are set correctly, the atoms will be set bouncing and the acceleration due to gravity can be deduced from the experimental parameters and Planck’s constant. The team managed to sustain this bouncing for about 100 cycles, which they say is the equivalent of dropping the atoms about 2 cm in a standard experiment.
Come in Here, Dear Boy, Have a Cigar
By the way, which one’s Pink?
The Factual One ponders The physics of… Pink Floyd?
What’s more interesting is the fact that the refractive index is generally not a constant. Within the same material it can be different for different wavelengths. Usually – but not quite always – higher frequency light experiences a higher refractive index. It gets bent harder. It’s not obvious at the level of classes I teach why this should be so. Since the details aren’t really the key issue, the main thing to remember whether it’s high frequency or high wavelength that gets bent most strongly. It can be difficult to remember, until I remind the class about this:
[cue Dark Side of the Moon album cover]
More discussion at The Quantum Pontiff
Countdown to Geekgasm
Self-Propelled Catapult
Meet the iFling