Index of Refraction

Laboratory eleven was trimmed to focus only on the apparent depth of an object below the surface of the water. 

 

 

Lavanaleen, Jeremy, and Lewis

 

This modification was made in part because the morning lecture combined pinhole cameras and lenses. The focus had been on the bending of light due to refraction. Mirrors just seemed like too much of an add-on that would distract and confuse from the core concept. 

 

 Jackleen

 

Summer is fast and furious, the course is moving at three regular term weeks per one summer week. Huge amounts of material are being explored by the students.

 

Merseny

This summer the class is not using the A204 computer laboratory. I required students to bring a scientific calculator to class. One student has a lap top computer.

 

Nayleen

 

Arthur and Raynard

 

Salinta, Joyleen, and Tracy

Joyleen and Tracy

The morning commute

My morning commute is not exactly high stress rush hour driving on smog-filled, twelve lane wide slabs of concrete surrounded by dingy and decaying metropolitan infrastructure.

My morning commute is an oxygen filled rush through an insanely humid, lush, tropical landscape. Of course the infrastructure here also decays and rather suddenly. Come around a corner a tad too fast and you might not be able to stop in time to avoid the decayed infrastructure or a roll-over accident in the road. Beach hibiscus tree tends to roll with time. Like a slow motion tumbleweed. Sometimes into the road.

Twenty-four hours after the first photo taken over my hood, at that same location, a Hibiscus tiliaceus tree had rolled, or fallen - your choice - into the road. Note the Acalypha wilkesiana (copper leaf) shrub on the right in both images. As another driver coming in from Kitti remarked, "Udahn kohlo!"

Spectrum tubes and CD spectroscopes

With no access to the computer laboratory for laboratory ten, I opted to focus on spectra. Summer 2010 I built the laboratory off of a morning lecture on colors, color vision,color blindness , achromatopsia, color constancy, retinex and GIMP. This summer the delayed start put laboratory ten on the Tuesday behind midterm and after the DVD Inconvenient Truth was shown to the class on Monday. This meant that I had to cover the midterm and lab hand-back notes along with spectrum material. So I dropped the color material and focused on the electromagnetic spectrum. 

Lavanaleen and Arthur examine the spectrum of hydrogen

In the laboratory session the students worked with CD-ROM based spectroscopes. The class had six to work with. I built one in class so the students could see the construction process. 

After viewing the continuous spectra of the sun, I dug out a box of old spectrum tubes and a spectrum tube power supply also from 1970. Exposed electrodes. 5000 volts. Probably time to buy one the newer units with shielded electrodes or the even newer models without through-the-glass electrodes.

I pushed the 30 second recommended time limit, running hydrogen for up to two minutes at a stretch. This summer I experimented with having the students color the spectrum. Bear in mind laboratory eight did not draw clouds this summer, so the students had not had the often negative experience with crayons and clouds.

Sucyang and Nayleen work on sketching the spectra of the sun, a candle flame, fluorescent lights, and ionized hydrogen plasma.

Some students felt that they could not color, so a coloring expert was brought in and on hand to assist the students who needed help selecting and using crayons. If nothing else, her presence, coloring skill, and age, left the college students with little to complain about. Can you color as well as a second grader? 

Mary-ellen works on her spectra

Sucyang studies notes on the board while Nayleen continues her sketching

The interaction between the CD surface, the digital camera wavelength sensitivity, and color balance choices  being made by the digital camera yield images that do not accurately capture the colors perceived by the human eye. The rightmost band of this image of the hydrogen tube was distinctly purple.

The HyperPhysics site has an excellent diagram of the electron transitions that generate the above three spectral lines.

This image is also of hydrogen, but the way the disk diffracted the colors the high frequency purple band is on the left. The spectral bands are in the Balmer visible series. The red band is 656 nanometers, the cyan band is likely 486 nanometers, and the blue-purple band is probably 434 nanometers.

The tubes are unmarked - the labels fell off decades ago. A gas with a strong yellow spectral band - sodium perhaps?

The laboratory lasted just over two hours.

Speed of Sound

Section 091 began with a RipStik sine wave and continued on to consider a bouncing ball and waves on a light chain. I ripped the paper oddly, wound up with three sheets. The wave was pretty horrible, I found only one usable section on a 68 cm wide portion of paper. The data can be seen below.

In laboratory nine the physical science class synched clapping boards to echo arrivals to generate data that leads to measuring the speed of sound. The class began with my bounding a ball off of the back wall, the ball that I had used in the lecture in the morning. I think this really helped make clear the concept of the echo flying out and back. I measured the distance to the wall and back, I also timed the ball flight time. Then I worked out the speed of the ball. I think this helps make the lab below more concrete. 


a determination of the dry bulb (32°C) and wet bulb (28°C) temperatures. Using the tables from section 8.1, the relative humidity was determined to be 74%.

Maimai times ten seconds while Raynard and Lavanaleen count board claps. Lewis maintains rhythm with the echoes. Mary-ellen and Tracy record data while Kemble and Arthur look on.

Mary-ellen Kerman enters data on behalf of the class

The value that I learned long years ago in school is about 20 m/s slower than the usual sound speed on Pohnpei, due primarily to temperature. On a crisp fall day in the midwestern United States the text book value of 330 m/s is fairly accurate. On Pohnpei sound never moves that slowly.

Joyleen Isaac takes a turn measuring the distance

This summer I opted to use the surveyor's wheel in lieu of using a GPS as I had not introduced use of the GPS to obtain distances in meters during laboratory seven. With the wheel there was no need to discuss the issue of errors in satellite receiver measurements. 

The instructor takes a turn at the surveyor's wheel

Oddly enough, the class obtained different clap counts. This is reflected below in some of the data which was gathered.

Location	Claps	Time (s)	Distance (m)
At the wall		0	0
Building B	32	0.31	102
Building B	37	0.27	102
Building B	40	0.25	102
Old faculty	24	0.42	121
Old faculty	27	0.37	121
Bookstore	21	0.48	169
Bookstore	22	0.45	169
Gym	10	1.00	304
Gym	11	0.91	304

The class worked down the main entrance road. The 304 meter out-and-back from the back of the bookstore to the gym was the longest flight distance.

Jackleen Miguel, Joe-ann, and Nayleen record data. Jackleen proved to have a particularly keen ear for echo synchronization.

			Percent error
Slope	309	m/s	-11.90%
Linest 0	327	m/s	-6.57%
Theoretic	350	m/s

Using the SLOPE function the data produces a speed of sound that is 12% low. Arguing that (0, 0) must be true and using the LINEST function to force the y-intercept to zero results in a slope of 327 m/s, only 7% below the expected result for the sound speed. Given the basic nature of the equipment used - boards 
being banged in synch with an echo by hand and ear, these results are excellent. The new, larger and more reliable stopwatches were a real plus in this laboratory.

The downside to using a linear regression is that the farthest out point dominates the slope value. Thus a slow synch off of the gym dropped the overall value. While longer distances would seem to be more accurate, the reality is that keeping a beat that is out at roughly one second is difficult. The overall average is 343 m/s which is only 2% low. I prefer to continue the focus on linear regressions, but the average usually outperforms the slope in laboratory nine.

Kemble times while Jeremy and Raynard keep count. Arthur looks on.

Anti-Fog Laboratory Eight

Mostly inspired by my own vehicle, but also in part inspired by MythBusters, I decided to test anti-fog options for cars without air conditioning in the marine rainy tropics. I opened the laboratory by coating both sides of one piece of glass louver with Rain-x Interior Glass Anti-Fog. I intentionally kept the bottle obscured behind items on my desk and I did not draw attention to what I was doing. I put the Rain-X coated glass and an uncoated louver into a stand-up freezer for thirty seconds. When I took out the louver pieces, one fogged up and the other did not.

Tracy applies ammonia to both sides of a piece of glass

The class, which had not been paying any attention, was now puzzled by this occurrence. A quick poll found that roughly half the class was acquainted with local cars in which the air conditioning did not work - the primary if not only choice for clearing a foggy windshield in the tropics. Heat will also work, but at 28° C (82° F) few people want to run the heat.

Nayleen places her glass pieces in the freezer

An instructor named Singing-Eagle, a native American, once referred to the cars on the island as "res wrecks," short for "reservation wrecks." Cars that were not necessarily street legal outside of a reservation. Fixing the air conditioning on my car would require parts from Japan that would exceed the original purchase price of the seventeen year-old vehicle. My car is not alone in its air-conditioning deficiency. Many students were accustomed to trying to wipe fog from the inside of the windshield with their hands.

Arrangements inside the freezer, wood blocks and a brass spring

I then revealed to the class that I had used Rain-x Anti-Fog. I also noted that the Rain-x had cost $5.49 at the local island Ace Hardware. And that I had bought the last bottle in stock. I then suggested that there might be local alternative anti-fog compounds. A few students, when asked, were familiar with spitting in their face mask to keep it from fogging when snorkeling. Of course, spitting all over the inside on one's windshield might not appeal to the other passengers in the car.

I then revealed that I had a variety of compounds we could test for anti-fog efficacy, including some that would require rubber gloves to apply and thus might not be as useful as anti-fog compounds due to practical safety reasons.

As the class progressed, pieces had to be kept in the freezer sixty seconds and longer. Opening and closing the freezer caused the interior to warm appreciably.

Results were recorded on the board. 

Results. Uht is banana.

Hand soap and dish washing detergent appeared to be the most promising in terms of being widely available, safe, and effective. Some compounds, such as Drano, caused the surface to become evenly wet, yielding a "clear" surface but wet which would distort the road. Not to mention the risk of splashing sodium hydroxide in one's eyes or on oneself when applying the liquid to the windshield.

The laboratory hand-in was only the table, nothing else. The lab lacks a good linear regression or other mathematical model, but is potentially useful to the students in their own daily lives.

Note that the morning lecture remained the standard 081 presentation on humidity, condensation, collision, coalescence. This summer, however, features no cloud quizzes and no cloud material.

Before Blogtime: Center

06 February 1993

Every evening the center of the world is Queen's Park, Port of Spain, Trinidad. Queen's Park was originally the British royal grazing lands outside of Port of Spain, until Port of Spain grew up and around the vast grazing lands. Now Queen's Park is perhaps the largest in-city park in the world, containing dozens of cricket and soccer fields along with a complete horse racing track and stables.

Every evening over a thousand Trinidadians come to the park to play, to lime, and to exercise. Around the edge of the park runs a wide sidewalk, carrying walkers, joggers, and runners in both directions around the park. Along the sidewalk vendors sell food from every corner of the world, Caribbean, African, East Indian, American, Filipino, and French foods are all available along the way.

Walking and jogging on the sidewalk are people from every continent on the earth, with the possible exception of Antarctica. As the sun sets warmly on this multicultural parade around the grassy park, the center of the world pauses and walks a lap around the park.

The park was only empty once, during a strange coupe attempt by a chap named Abu Bakr. I was there, in a hotel at the very edge of the park, near the television station of which Abu was in command. From the upper stories we could see Abu's men on the television station rooftop with their M16s. Shortwave kept claiming Abu was armed by the Libyans, but I saw no AK-47s, and when it later turned out that Abu had bought all of weapons at an arms show in Miami, I was not surprised. During those few days the park was empty as bullets whistled between the buildings of the city.

Near the end the Trinidadian army came running across the park, punctuated by choreographed rolling and diving with their own M16s. We stood out in front of the hotel watching with some amusement as we had already determined from our own observations that all of Abu's men had pulled back to the television station.

I did not get to see the park return to being the evening center of the world as we fled on an Air Venezuela flight to Caracas before the army imposed curfews were lifted. I need to return someday to reassure myself that the world is walking around the edge of the park again.

In the meantime, here in Pohnpei, we proudly maintain our own pale imitation as Micronesians and expatriates of many countries gather each evening to walk and jog around the Pohnpei Island Central High School track.

Every other evening after jogging in the foothills above the family home, I swing past the track and put in couple laps with the rest of the exercisers. There is no food, and a lap is only 400 meters, but we enjoy a fantastic view of our volcanic tropical rain forest carpeted mountains and our rain washed clean air.

Introducing Sine Waves in Trigonometry with a RipStik

In order to introduce the graph of a sine wave in MS 101 Algebra and Trigonometry, chapter 6.4 of Larson's text of the same name. This was done out on the porch.

 Starting my run towards a sheet of paper on the porch.

 The towel is wet and dyed with blue food color. Only after I did these runs did I discover that the cement was rough enough to effectively emboss the sine wave into the paper without the need for the wet towel. I would later successfully perform a "dry imprint" using the RipStik in my physical science class two days later.

 The RipStik produced a wavelength of 32 centimeters at a period of 0.4 seconds with an amplitude of 4 centimeters. WolframAlpha was used to then generate a graph of the function. My inability to determine how to control the aspect ratio results in an exaggerated vertical axis for the graph.

Larson does not introduce wavelength, focusing instead on period. Larson also leaves the calculation of the frequency for a homework problem involving a tuning fork (number 77 in the seventh edition, number 91 in the eighth edition). I introduced both of those concepts along with the product of the frequency and wavelength producing the wave speed.

My Micronesian Household

My household is at present provably un-American. Less than a thousand families in the United States have a family composition identical to mine.

 

The New York Times applet helpfully suggests that I remove household members, possibly to become more American. If I remove my sibling-in-law I actually crack the surface and emerge as a one in 1608 households in the United States.

 

The numbers climb even higher if I toss the child and keep the mother-of-the-child, joining the ranks of 88,891 households in the United States.

 

Of course, returning to a nuclear married family puts the numbers up by a factor of 91 times higher - a huge gain. As married-wth-two-children my family joins over eight million other families. We would become downright common.

The applet notes that the greatest number of households with the above composition make between $75,000 and $150,000 a year. 

If I were to add back in the one currently abroad, however, the numbers slide back down again.

 

I like that my family is unique, there is nothing common about us.

How about your family? Are you simply running with the pack, undifferentiated from the norm? Or is your family also unique?

Our March 2011 configuration was not only also  beyond the tool's ability to calculate, the tool would not even allow me to enter this configuration!

Finding Binky amid latitudes and longitudes

With the lecture section beginning at 9:30, immediately on the heels of MS 101 Algebra & Trigonometry, hiding was problematic. The solution was Binky. I hid Binky early in the morning and then was, for the first time, able to accompany the class on the hunt for Binky. "Binky! Binky! Where are you Binky‽"

While introducing the GPS receivers I also demonstrated to the class the GPS capabilities of a FujiFilm FinePix XP30 GPS digital camera. For the image of Nayleen and Sucyang the camera reported a position of N 6° 54' 32", E 158° 09' 40" (N 6° 54.534', E 158° 09.666').

Five teams set off on the hunt for Binky. Merseny watches the changing latitude and longitude.

The class would enjoy cloudy but rain-free skies throughout the day.

At the main road Merseny confers with Sucyang. The paper contains the latitude and longitude at which Binky is hidden, N 6° 54.656', E 158° 09.439'.

Nayleen follows along.

Arthur heads off-road into the wet reh padil grass. Binky is nearby, tucked amid the tall grass. The teams will have to get to the exact grid coordinates in latitude and longitude to actually locate Binky.

A small knoll at the Binky location complicated locating Binky. Jeremy would walk right by Binky without seeing Binky amid the tall grass. Lewis, working up the knoll from another direction, would be the one to spot Binky and effect the rescue.

Jackleen would wind up with Binky.

Jeremy operates the surveyor's wheel for laboratory 072 latitude and longitude.

Raynard and Jackleen follow a line of longitude northwards.

Merseny corrects her course near the library.

Maimai steadfastly followed her line of longitude right through the swamp on the west side of the library.

Maimai and Kemble headed down the library slope.

End point at the road.