Ripples in the Pool

On Saturday, my mom and I decided to go for a swim at the pool; since swimming season ended, I haven't exercised at all, unless you count our many exhausting but enjoyable band rehearsals, so I needed it. But as I was leisurly walking/floating back to the wall after trying some distance breastroke pulldowns, I thought to myself, "Hey, I wanna try making ripples like in Physics!" I then began playing with my fingers, hands, and the already ripply surface of the water to try to see the two circular waves converge and form higher troughs and peaks due to constructive wave interference, as well as regions of destructive interference. As the waves first began to expand outward, I noticed very large peaks forming, and then more formed, I saw the regions of destructive interference. Had I been able to freeze time and place a sheet of waterproof paper to record the heights at the convergence region parallel to the connection of the radii, I would have seen regions of both constructive (in a 180 degree phase difference with each other, as one peak hits with one trough on the other)and destructive interference. These regions would correspond to the light and dark regions of double slit interference with light as well. Wow, I guess there's one more reason to go to the pool on weekends: Physics in action! :-)

Mirage

In OPTI-GONE Int.'s contraption Mirage, two concave mirrors are placed one on top of the other, with a small opening at the top of one. This contraption forms a floating image inside this opening using the mirrored surfaces inside. After much consideration and learning about concave mirrors, the answer to why this works seems to lie in the focal legnth of the mirrors. When light enters the opening, it hits the object on the bottom, reflecting off the object and radiating out into the mirror region. In the cases of light rays like the ones diagramed, they will bouce a few times, hitting a mirror and refracting at the same angle of incidence, continuing until it either happens to exit the region, perhaps without even touching the object, or hitting the bottom mirror parallel to the principle axis. When it does, the light will then refract to the focal point, which for these mirrors is placed either inside the opening for the bottom mirror or at the center of the bottom mirror for the top mirror. This results in the fact that nearly all light will eventually converge on the focal point at the opening, creating an image to the human eye that should originate in what is actually thin air. The fact that the object sits on a mirror also results in an image of the image of the object on the bottom mirror appearing at the opening as well. Pretty cool!

Infinity Me's!!!!!

When I was little, I had a fascination with mirrors. I guess I liked Physics from a very young age! :-) I had three favorite things when it came to mirrors: two planar mirrors at right angles, two parallel planar mirrors, and three folding planar mirrors of the same size. In my travels through the various malls and dressing rooms of California and Hawaii, I found many instances of all three. But my favorite memory was of a particular dressing room in a department store here (I think it was JCPenny's). I was playing with my three reflections (we were identical quadruplets!) when I discovered that the mirrors, unlike other dressing rooms I had encountered, could move on their hinges and close to form a triangle, just big enough to fit me. :-) When I closed myself in this triangle, I noticed that I increased from quadruplets to quintuplets to sextuplets to septuplets, and so on, until there were infinity me's. However, we were not all in a big circle, there came a point where the number in the circle stopped increasing, and I noticed many other circles around me. It was fascinating. Now that I think back on this experience with some Physics knowledge, I realize what was happening. When I faced a corner, there was an image of me on each of the mirrors, and as I closed them, secondary and tertiary images began to appear as the mirrors reflected each other's light and their images. When the angle was as small as it could get in the triangle, the mirrors stopped reflecting new images. But there were also circles of images coming from the other two corners in the triange, showing me from different sides in the same manner. The mirror opposite each corner would then reflect the image of the circle of me's, then reflect the images of the images from the other mirrors, creating an infinite field consisting of three different orientations of me's. I tried to illustrate my fascinating experience from above(but not with all the reflections, of course!), adding in a pink bow so I could trace light rays. It was very fun. It's funny, I never got into curved mirrors when I was little. Maybe that woudl have been too complicated for me then. Oh well, I still enjoyed mirrors. I wonder where those mirrors are now...

Clicky Watches

A few summers ago when by uncle and cousin came to visit us from New Jersey, my uncle would sit in our chair by our computer and shake something that make a small clinking noise. Upon closer inspection, it was his watch. He said that it didn't have a battery, and that shaking it kept it going. At the time, I didn't understand what he meant, but I remembered this this past week as we explored electromagnetic induction; his watch must have had a magnet and a solenoid in it. The shaking sound must have been a magnet, moving back and forth into and out of the solenoid. The magnet's magnetic field would have turned the solenoid into a magnet, alternating the poles to repel then attract the magnet as it moved in and out respectively. The force of the moving magnetic field on the electrons in the metal solenoid would generate an alternating current, building up charge that would eventually go to power the battery. I'm not sure how the charge was stored, as capacitors only seem to be able to discharge charge (:-) )in large, fast, quantities that would probably do to the battery something similar to what happens to galvanometers when too much current runs through them (not a good thing).

However, I guess that the generated current is not that much, as my uncle still had to sit and conscienciously shake the watch; the natural motion of his arm wasn't enough, I guess. Great idea, but I wonder if it was more trouble that it was worth. (My watch has a regular battery :-) )

Cheryl Hayashi: "Spiders, Silks, and Me"

On Tuesday February 5, I attended the lecture by Cheryl Hayashi, describing her experience from high school graduation to finding her career passion to her present day research. At first, studying spider silk seemed like an obscure profession, but after her explanation of her road to this career, I not only found it fascinating, but was also inspired to finding my own passion.
She began her presentation by telling of her path from high school to finding her career; this section perhaps had the most impact on me, as I’m currently pondering what I want to do with my life and what classes to take next year. The fact that she found her life’s passion from a requisite class and a small part time job really says that anything is possible. It also encourages you to take every opportunity presented to you, for you never know what may turn out to be your life.
Aside from the inspiration, I also learned a lot about spider silk that I never knew before. I had known that silk was comparatively much stronger than many things we consider very strong, but I didn’t know just how strong that was until I saw the comparison. I was also surprised to learn of the many different types of silk that one spider can produce. And a hundred and fifty yards of silk from one spider! Wow. I hadn’t known there was so much to just spider silk alone; and as she said, one answer brings up ten more questions, like: I wonder what else there is to study that contains more than meets the eye? Perhaps one of those could be my passion. I’ll just have to wait and see.

Homework By Lamplight...

As I was sitting doing my Physics homework wondering what I should do my blog on, I began doing a sample problem about current, power, and resistivity. All of a sudden, it his me- I have a very close-at-hand example of all three of these: the lamp next to my computer. It has a bulb that contains two filaments, and the lamp is made in such a way that it can produce three different levels of light: one filament, the other filament, and both together. As I worked on problems pertaining to legnth of the resistor, cross-sectional area, resistance, power, and current, I began to wonder how the bulb worked from a Physics standpoint. This is what I have decided: there are two possibilities for this bulb. The first possibility (depicted above) is that each of the filaments have different legnths, but same cross-sectional areas. Since R=(coeff.)L/A, the filament with the longer legnth would have a greater resistance than the shorter one. Then since P=(I^2)R, and I(current) is the same for each of the filaments since the current comes from the same source, the power in the longer/higher resistance wire would be greater, resulting in more electron movement and more transfered energy to the filament's atoms, and therefore more light.

The second possibility was that the filaments have different cross-sectional areas but the same legnth. Then, since R=(coeff.)L/A, the filament with the smaller cross-sectional area would have the greater resistance. Then since P=(I^2)R, and I is the same for both, the power for the thinner filament would be larger, resulting in more collisions and more light.

There is actually a third possibility: the filaments could have both different areas and legnths. However, companies may want to save money by using the same wire, as well as try to increase the longevity of their bulbs by using the same thicker wire with different legnths. Or would they want to use the thinner one so that the thinner filament will break more quickly so consumers will have to buy more? :-)

Blue Sparks

Perhaps some of you who read my post a few weeks ago saw my mention of a large spark my dad created on our trip to Alaska. Well, here's more details.

If you have ever been somewhere dry, you know that static electricity is something to be feared. But on this trip to Alaska, we were staying in a hotel that required walking about twenty meters from our door to the elevator, all the way on carpet. One morning, my dad, being still a young boy at heart, decided to drag his feet along the carpet to see how much static/electrons he could accumulate. By dragging his feet, he accumulated extra electrons, giving himself a net negative charge, increasing with the amount of dragging. Having discovered that the panel on the side of the elevator was grounded, he slowly moved his hand towards the panel. However, he had accumulated so many electrons and potential energy that all of the excess electrons quickly left him for the grounded object, even before he touched it. The large discharge of potential energy, energy converted to kinetic energy for the quickly moving electrons, caused a visible spark coming from my dad's finger, quickly followed by an exclamation of "OUCH!" along with a slight jump. The electrons then probably were transfered to the ground, where they quickly spread out equalizing the charge, effectively canceling it out. Perhaps more electrons moved within the building back to the momentarily positively charged floor, so some electrons going to the ground ended up back in the building. But, like I said, the spark was a bluish color, and very bright. After that, my dad and I discovered that walking while rubbing our hands on the wooden handrail, as well as touching the elevator panel through our jackets, lessened the severity of the shock. I'm glad I don't have to do that on a regular basis. If we ever go back, I wonder if my dad will have learned his lesson, or if the young boy inside of him will prevail again? :-)

P.S. My mom was folding laundry once again (thank you, Mom!), when a sock which was held onto a shirt by static electricity from transfered electrons from the dryer came flying off when she shook it and landed right back in the pile without her noticing it. It was hilarious. :-)