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...