Blog 14-Reflections

While we were waiting to perform in Advance Theater's Shakespeare Festival, my friends and I were taking pictures to help the time pass more quickly. In the photo above, several different physics concepts are pictured.  

The first is electricity.  The lights behind us are in parallel circuit. Some of the bulbs are out (probably the filament burnt out), but the rest of the lights are still able to be turned on.  

The second concept is reflection.  The mirror behind us reflects all the light from the objects in front of it.  From this angle, the photographer is visible in the reflection because her object's (i.e. her body) incidence angle is visible in the reflected angle.

The virtual images are of an equal distance from the mirror as the actual objects.

Blog 13-BEACH DAY

A few weeks ago I went with some friends to the beach. When we went into the water, I brought my waterproof (only up to ten feet) camera with me. 

Anyways, we took a bunch of pictures that day, but I didn't really go through them until recently. One of the pictures that I thought belonged in the trash bin actually shows a great example of refraction. In the picture below, part of the lens is out of the water and part is below the water. The viewer can see the way light bends in the different mediums.

In image in the water appears larger than the real object. In addition, this light is bent differently in air than water due to the different indexes of refraction.  The index of refraction of air is about 1 whereas the index of refraction for water is 1.33.  By using Snell's Law, we could predict the angle of refraction at which the rays of light were shot off from the surface of the water.

Also, it is slightly difficult to see, but this photo also exhibits total internal refraction.  The image of my friend's body is reflected on the surface of the water. However, the angle of refraction is too large, so some of the light rays are reflected back from the surface or the water and are sent downwards/along the surface of the water, as shown.

Blog 12-PORTLAND :)

Last weekend I went to Portland, Oregon, for a four-day national high school journalism conference with two friends and two teachers.  Though we are constantly surrounded by physics, the City of Roses provided some excellent examples.

We happened to arrive on the day that two airlines, Horizon and Alaska, officially merged.  Thus, all of the staff on the airlines were walking around the airport passing out roses that announced the merge.  I set the rose down on a newsstand and was reminded of the way light affects color.  The red rose petals were absorbing the green and blue portions of the white light of the sun and reflecting only red light.  The green leaves and stem were absorbing the red and blue light and reflecting green light.  This is an example of how the color of an object is dictated by what parts of white light it absorbs or reflects. In the picture, you can see the white light hitting the rose, and you can see the color it reflects.

At the Convention Center, a large pendulum constantly swings from side to side.  It changed direction of its swing depending on the rotation of the Earth.  In addition, it is a perfect example of tension. The tension in the cord allows it to hang without falling, yet it is strong enough to allow the orb to move freely.  I took a short video of it so that I could post it on my next blog.  Disregard the background noise.  I don't know how to take it out.

Last, we went to the Market on Sunday.  At the market, many street performers were displaying their talents, whether it be in music, art, or dance.  A pair of boys, one about our age and one about 13-14 years old, did a drum duet of sorts on makeshift drums.  The reason that their music sounded appealing instead of cacophonous is because waves pass through each other rather than interfering with each other.  Using this idea, the boys could play very upbeat music without driving away their listeners.  However, they probably did not realize it took such good physics to produce such a sound.

Overall, the trip was AMAZING!

Blog 11-Hydroplaning

This weekend's wind and rain were especially heavy in Manoa, creating rather unfit driving conditions.  However, I ended up driving my family around because they felt I should practice driving in "unfortunate conditions."  Due to the amount of rain that accumulated on the streets, I had to drive more slowly in order to avoid the possibility of hydroplaning.  Hydroplaning occurs when there is a layer of water in between the road and a car's tires, causing a driver to lose control of his or her car and potentially end up in a hazardous situation.  In order to avoid such a situation, drivers need to take several physics concepts into consideration.

First, lack of friction is the cause of hydroplaning.  Thus, in order to help prevent hydroplaning, tire manufacturers added many grooves on the tires in order to try to disperse the water from under the tires, thus increasing surface area and giving the tire more friction with the road.  In the picture below, the water is being sprayed from under the car tires, which shows that the grooves in the tires must be working.  

Second, speed and acceleration of the car affect the likeliness of hydroplaning.  If a car is going 60 mph, accelerating, and there is a large puddle on the road, there is a higher possibility that the car will hydroplane than if the same car was driving at 20 mph and slowing down through the same puddle.

Although hydroplaning is unlikely to occur, it is best to take extra precautions during a heavy downpour.  Driving slowly and with extra caution will help a driver maintain control of his or her car.  In addition, as a driver, you should make sure your tires have the proper amount of air in them and make sure the tread of your tire is not worn.  These factors use physics concepts in order to prevent the hazardous situation of hydroplaning.

Blog 10-Rainbow

This weekend was pretty rainy in Manoa.  At around 5 pm when I went into my living room to grab a snack I noticed that there was a rainbow across the valley.  Manoa is so rainy that rainbows are, for the most part, a daily occurrence, although on most days I am not at home when the sun is up.  

Anyways, rainbows are a fine example of light refraction.  As everyone knows, in order for a rainbow to occur, water drops and a light source must be present.  The light source must be at a lower angle in order for the rainbow to occur.  The water drops refract the light, then the light is reflected off the back of the drop, and then the light is refracted yet again as it is leaving the drop.  The different colors of the rainbow occur due to the different wavelengths.  The raindrop acts as a prism and refracts the white light into the different colors. As this white light is refracted through the raindrop, the wavelength of each color comes into play.  Red has the longest wavelength of the colors, and violet has the shortest wavelength.  

Unfortunately, rainbows are incorporeal (vocab anyone?).  There is no pot of gold at the end of a rainbow because rainbows are not solid.  A rainbow is only visible if the viewer has their back to the light source and if there is some type of water droplets in front of the viewer.  

In the picture above, the sun's light is the white light source.  I am the viewer, the sun was behind me (and to my right), and it was raining on the other side of the valley. 

Blog 9-Fish eye lenses

Last weekend some of my friends and I went to the beach.  Earlier that day one of my friends had bought a "fish-eye lens" for her camera.  However, her camera isn't a fancy SLR camera--it is a waterproof point-and-shoot type.  Her fish-eye lens was a peephole for a door that she had bought at a hardware store.  However, since it was a convex lens with similar properties to the professional lenses, it produced a fairly similar result:

A fish-eye lens is a converging lens.  This means that the light will focus on a focal point (i.e. one point instead of diverting light in multiple ways like a diverging lens).  Most converging lens diagrams look something like this:

This diagram is from Wikipedia (http://en.wikipedia.org/wiki/Lens_(optics)).  In this diagram, the rays converge on a single focal point.  This is similar to how a peephole lens works.  The rays of light (on the left side) enter the lens and converge on a single point.  In the peephole lens, the focal point is the area where one would place one's eye.  

Attempting to attain the proper effect of  a fish-eye image with a door peephole and a point-and-shoot camera is much harder than it seems.  Since the peephole is made for seeing objects in a broad but near area, the camera user must zoom in.  The barrel of the lens also makes the image appear farther away due to the length of the peephole lens from the camera lens.  

The shape of the lens distorts the image due to its extreme curvature and the layers of lenses.  In the top photo, the edges of the image are much more circular than in real life.  Photographers sometimes use the fish eye lens when shooting landscape photos because it suggests the circular-ness of the earth.  However, their photos turn out a lot nicer and usually lack the black area around the circle. 

I don't really understand much about the other physics-properties used in these types of lenses, but I look forward to learning about it later on in the year.

Blog 8-Seesaws

After a swim meet at Punahou, some of my friends and I went to play on the playground.  One of the fun things to play on at Punahou's playground are the seesaws.  Instead of rocking back and forth on them, as all the other children were doing, we, being physics/AP physics students, tried to balance the seesaws.

At first, we tried with only two people on the seesaw.  In this picture, Kevin and I are on the seesaws.  Since our weights are about 30 pounds different, he had to sit much closer to the fulcrum than I did.  By doing this, we were able to balance the torques on both sides of the seesaw.  If we were in a classroom, we would have been able to use the equation: TORQUE(ccw)=TORQUE(cw).  Since torque=force x radius, we could have set up the following equation: (106 N)x(2.5 m)=(135 N)x(r).  Kevin had to shift his center of mass to 1.9 meters away from the fulcrum in order for the seesaw to be balanced.

After we balanced the seesaw with two people, my other friend jumped onto my side of the board.  This time, Kevin had to shift his center of mass backwards in order to balance the board. Again, if we were in a classroom, we could determine the different torques on each side of the board: Fr + Fr=Fr.  Thus, (106 x 2.5) + (95 x .15) = (135 x r).  In this case, Kevin's center of mass is at 2.06 meters.

Blog 7-Liquid Fury

At the Kalani Invitational on Saturday, my friends and I participated in the Liquid Fury relay.  As intense as this may sound, it is actually a "fun" relay where teams of six (although the number of participants really doesn't matter) compete to be the most entertaining for a blue trophy. My friend brought a stand-up surfboard, two paddles, and an inflatable walrus.  Our plan was to have one swimmer (Kacy Johnson) drag the rest of us around while we balanced on them. 

For the first leg of the race, Kacy pulled Kevin across on the board, and for the second, he pulled another guy (Jacob) on the walrus while Jacob paddled.  However, Kevin was much more successful at keeping his balance for several reasons.  The board has a much greater surface area, its center of mass was central and low, and it was meant for people to be on it. In the above picture, it is easy to see that Kevin can balance easily and move quickly through the water.  The inflatable walrus, however, was much smaller, had a higher center of mass (since it had a head and is in a sitting position), and was not intended for humans to ride it while paddling.  Jacob struggled to maintain his balance on the walrus, and fell off of it several times.  The picture below is one of the times that Jacob fell off of the walrus.

For the last leg of the race, five girls piled onto the surfboard and made Kacy and Kevin push/pull us.  The picture at the very top of the page shows the five of us on the board.  However, part way through the lap Kevin got distracted by the walrus floating by so he let go of the board.  His upward push on the board had kept the torques balanced (net torque had been zero).  Since he let go, the back end of the board began to sink, so we tried to scoot forward towards Kacy.  

If we were to draw a FBD for this, Kacy would be the fulcrum and his arm would have tension at a diagonal (since he is pulling us forward and providing an upward push to help keep us afloat).  The water/board provides an upward push due to buoyancy.  Each girl would have a different torque since we all have different masses and were different distances from the fulcrum.  The board’s center of mass would also have a downward push. 

Thankfully, we did not flip (lengthwise, later we flipped sideways because my friend started dancing while standing on the board).  The torques were unbalanced, yet we were still able to stay afloat due to the buoyancy of the board and some good physics (the front end of the board was well supported but the back end was sinking). You can see the uneven support in the picture above.