Blog 14: A Year of Physics in Review, Through Lenses

How often during this year did our difficulties seem to be viewed through a converging lens - the image of problems so large and real, turning our worlds upside-down?

What we once thought of life.

As this year draws to a close, I now understand that the present passes us by with astonishing speed. I look back, and everything I knew of myself and the world enters a diverging lens of vast curvature and emerges virtually infinitesimal.

The earth now.

No matter, for the image we see will always be sharp, regardless of its size in our expanding minds.

Early on, I wanted to switch to AP Physics. I believe I made the right choice to stay here. The pace of AP has warped the students' minds. I have taken concepts and turned them to these retrospective thoughts.

AP students turned them into a doughnut cannon.

 

Wait, what? Okay.

Blog 13: Black Lights In Space

Okay, so we weren't really in space, but we were all pretty up there on the night of the Neon And Space Adventures dance. That's because we were on the third floor of Weinberg!

Yeah, there were some questions when I heard about the dance venue - why would we want to have a dance inside the school? Would I get to dance in Mr. Park's room? 

He didn't look too happy about that idea.

In truth, I wasn't interested much in NASA as a non-dancer. I was drawn by the intrigue of a third-floor dance, and stayed for the physics.

The notion of having a neon-themed party would be nullified without a crucial technology: the black light. This "black" light, of course, is a misnomer; as black is not an actual color (but rather the absence of visible light), this bulb is actually shaded in the upper regions of violet-wavelength light.

Technicalities aside, the black light works by employing a phosphor-coated covering over a fluorescent lamp. This covering absorbs all visible light wavelengths, as well as UV-B and higher forms of electromagnetic radiation, while allowing the highest-energy violet and UV-A waves to pass through.

Quite the selective process.

So how does the black light cause other things to glow, such as every single piece of lint on your black shirt? It turns out that these glowing objects contain external phosphors as well. By exposing these objects to the filtered black light, they reflect this light as well. 

I spent the night watching these lights. At the next dance I will ponder glow-sticks.

I'm on the pursuit of happiness, and I know / Everything that shines ain't always gonna be gold / I'll be fine, if it's phosphors.

Blog 12: Guitar Physics

Many types of waves surround us constantly: light waves, water waves, radio waves, etc. Perhaps the most enjoyable waves of all, however, are sound waves. Of course, these pleasant sound waves must come from somewhere. 

Enter the Epiphone Masterbilt AE-500ME.

When playing my sound-wave-generator, I did not know any of its properties as they related to physics. Now that I finally do understand all of my guitar's secrets, I can go on and on about them. 

Wave frequency in strings: When I play an open string, I create a standing wave in the string with a frequency that is dependent on the tension of the string and its length (f = √ F / (m /

L) ).  The reason each string sounds different is because each has a different mass - the low E has the highest mass, thus increasing the value of (m / L), thus reducing the frequency. 

Whenever I play a note by pressing on one of the frets, I am reducing the length of the standing wave, thus reducing the value of (m / L), thus increasing the frequency. Increasing the frequency, of course, increases the note's pitch, resulting in a higher note.

Harmonics: If I press my finger lightly to the 12th fret of my guitar on any string, I produce a harmonic that is one octave higher than the fundamental frequency (open note) of the string. However, the 12th fret isn't the only place where I can produce a harmonic; the 5th, 7th, and 19th frets also create harmonics. In fact, the 5th fret will produce a harmonic that is two octaves up from that of the fundamental frequency. 

Beat Frequency: 

As heard in the video, an irregular wave is produced when I slowly bend the string so that its frequency differs slightly from the other. This is called a beat frequency, and although I did not know why it was produced, I used it to gauge my tuning since I began playing. This method is not the best, however, because the human ear cannot discern between minute differences in frequency (as an electronic tuner can). 

Now that I know the physics behind my guitar, I will always be amazed at how a few strings of metal stretched over a piece of wood can be an endless source of knowledge, fascination, and enjoyment. However...

... I am not sure that physics has improved my guitar playing. When shall science make me a master shredder? Only time will tell.

Blog 11: "MagSafe," or US Patent No. 7311526

Prior to the January 10, 2006 introduction of the MagSafe connector by Apple, Inc., laptop users worldwide were faced with the potential horror of this:

This gory carnage brought to you by http://en.wikipedia.org/wiki/MagSafe

A terrible disaster awaited every avid Macbook user: if the power connector was pulled out at any disagreeable angle, the entire male-female connection would be ruined. And God help you if you happened to trip on that forsaken wire.

The MagSafe revolutionized laptop recharger connection port safety with the brilliant innovation of a magnetic connection between port and connector. But how would such an invention work? 

Before I answer the question, a few action shots.

Always practice safe charging.

A fool's postulation would insinuate that the connector is charged with a 'north' magnetic charge - and the port 'south,' or vice versa - thus creating a magnetic attraction between the two. This could not possibly be true, for a magnetic monopole is a hypothetical creation still ten million years away from the MagSafe's construction.

Therefore, the only plausible construction of the MagSafe would be for either the port or the connector to be magnetically charged, and the other made of an uncharged yet ferromagnetic material. And by 'ferromagnetic material,' I mean a material that contains atoms with elections that have unpaired spins that create domains that align when in the presence of a stronger magnet. 

But which one is the magnet, and which is merely the ferromagnetic material? Well...

A few paper clips enhance my understanding.

This makes sense, because if the connector was a magnet, it could pick up many bits of ferromagnetic material and create the potential for a short circuit. But short circuits are from another chapter.

Blog 10: Light Bulbs, Inc.

Light bulbs are not very interesting. In fact, they can be downright annoying to replace, especially if they're in hard-to-reach areas. So how could they possibly be interesting?


We've all seen the curly CFLs, the rod-like fluorescents, and the futuristic LEDs. But the most basic of all is the incandescent. And those are the most boring of all.


Not exactly. I found two different makes of incandescents, the typical lamp bulb, and a flood-light. It was an odd experience to hold these fragile things that have hung overhead and out of reach.

Light of my life.

Big boy.

Besides the obvious size and structural differences - the flood-light is top-heavy and its sides are heavily frosted to 'focus' light outward - something completely unrelated to physical form makes the flood-light brighter: wattage. 


Okay, the flood-light is 65 W while the lamp bulb is 52W. But what does that even mean?


Well, as with everything, the inside is what matters most. Within both bulbs are filaments of tungsten. However, the flood-light's filament is thicker than that of the lamp bulb. A thicker filament provides more room for electrons to move through it, and thus enables more current to flow through the wire with a given voltage difference. More current = more power = more light!


But how much thicker is that flood-light filament? Well...


Given R = ∆V / I = (ρL) / A   -->   A = (ρLI) / (∆V)
and P = I(∆V)   -->   P / ∆V = I ,
cross-sectional area A = (ρLP) / (∆V)^2.


So if both filaments have the same ρ and L, and ∆V is constant (at 120V),


Alamp = 52(ρL) / (∆V)^2
Aflood = 65(ρL) / (∆V)^2


Therefore, the flood-light filament is 1.25 times thicker than the lamp bulb filament. When we discuss filaments, we're talking about mere millimeters (or less!). So such a minuscule difference in filament thickness really impacts the brightness of a light bulb. 

FASCINATING.

FASCINATION x 2

Blog 9: Travel Voltage Converter

Once again reliving my memories of my trip to Vietnam, I now see the physics behind one of the most overlooked yet important pieces of travel equipment: the voltage converter. 

The many faces of an unsung hero

Because different nations have different power systems, the voltage that is contained in power outlets is not always the same. The voltage in Vietnamese power outlets is 220 V, whereas American power outlets run at 120 V. 

The voltage difference presents a major problem. If you plug in your American device, which is constructed to run on 120 V, into a 220 V outlet, there is a difference of 100 extra volts that flow into your device. That voltage difference, as we were warned by Mr. Brown (a trusty veteran of Vietnam travel), could cause the entire hotel to black out, and fry your device.

Now, what is more important here?

Wait - 100 V isn't very much, considering that a Van de Graaff generator can produce about 400,000 V. So how can 100 V cause such a stir?

Well, voltage is a ratio of energy to charge. The Van de Graaff may produce 400,000 V, but the ratio may be 40 joules / (1/10000) Coulomb. However, 100 V in a power outlet could mean 100,000 joules / 1000 Coulombs, which means that there is a large amount of electrons, and thus a large amount of energy. That is why 100 volts running through your device could mean doom for its circuitry. 

During our first night's stay, some idiot forgot to use a converter, so Tan My Dinh Hotel had a black-out. Though someone got stuck in the elevator, the worst part about the black-out was the absence of TV or air conditioning for an hour. Lesson learned - don't go traveling without a voltage converter!

Blog 8: ASIMO

Honda's ASIMO ("Advanced Step in Innovative MObility") humanoid robot is certainly an interesting piece of technology. While in Japan for a 12-hour layover (returning from Vietnam), our tour group had the opportunity to meet Mr. ASIMO. He greeted us with a few 'words.'

'What, is this blog late?'

"Of course not."

ASIMO was able to walk, run, use non-vocal expressions, and he could even dance. I'd say that makes him pretty human, because I definitely can't dance as well as him.

What made ASIMO incapable of ever being a human, however, was his peculiar stance: he could not stand still without having his 'knees' bent. 

"Am I not human? But I can cry..."

As it turns out, ASIMO, with all of his robotic gadgetry crammed into his back panel, has a center of mass located slightly behind his heels when he stands up straight. Therefore, the torque caused by his mass would cause him to rotate and fall over. To compensate, his designers forced him to be bent-kneed at all times in order to keep his CM inside of his support base and to protect his expensive circuitry. 

Thus, for self-preservation, ASIMO continues to be a bent-legged robot, suited for waiting tables.

Maybe next time, buddy.