Research Journal

May 10th, 2013

Today marks my last meeting with Dr. Noé of the semester. I have a rough outline of my report finished; I just needed to clarify how to do two calculations and also the proper formatting for my references. Dr. Noé explained how to do both to me and I am now very close to finishing my report. It's been a great semester and I am very thankful to Dr. Noé and my classmates for making this semester's PHY287 class, such an enjoyable one.

May 6th, 2013

I was the only one in class today, so I got some one-on-one time to work on my report with Dr. Noé. I started off the class by taking a measurement of the sun's direct intensity at bout 1:10 pm. It is a bright and sunny day with very little cloud coverage. I measured the sun's incident intensity on the photodetector to be 4.3mA. This is pretty consistent with previous measurements I've made for the sun's intensity.

Dr. Noé and I spent the rest of the class working on my report. We wrote an introduction to the report detailing how I got interested in my project and set up the different sections of the report. Dr. Noé informed me that our work is due on Monday, May 13th.

May 3rd, 2013

Today instead of meeting as a class in the Laser Teaching Center as per usual, I attended Angela and Carolyn's WISE presentations in the Humanities building. Their presentations were short and generally lasted about five to ten minutes.

I was impressed by the amount of material both of them had in their presentations. Both presentations were fairly good. Although, I found Angela's presentation a little confusing to follow because she used a number of technical music terms without explaining them and I do not have a background in music. Carolyn's presentation was very well done. It was very accessible and understandable, but still showed good science. It was really cool seeing Carolyn "open up".

April 29th, 2013

Today we mostly talked about Angela and Carolyns presentations for WISE on Friday. Their presentations are going to be in Humanities 3008.

Angela did show me how to upload photos onto our website from a Mac today. The command is spc (fill in where) rachels@laser.physics.sunysb.edu:public_html. To figure out (fill in where), you ctrl click on the file and select get info. I also figured out that on Macs, you can drag and drop the file into terminal and it will automatically fill in the files information. From there you can log into your account and then type in mv file name to move the file to another directory. [I now realize that my problem wasnt that I was using the wrong command, but that I was spelling the name of the computer wrong.]

I looked over Marissa and Debs reports to learn how to organize my repost. Dr. Noé said that my report should follow closer to the formatting of Marissas.

Use cd .. to move up a directory

April 26th, 2013

We took more measurements of the albedo of green grass today.

These measurements seem to suggest that albedos decrease with height. I believe this result was due to the grass being non-homogenous, rather than albedo being dependent on height.

April 24th, 2013

Today was URECA. I think it was a good learning experience. The two main lessons I learned were:

1. Do all of your homework ahead of time

2. Be proactive

Ill admit that I wasnt as invested in showing off my poster as I should have been (I was distracted by the large amount of homework my teacher assigned the night before). For the future, I am going to make sure all of my homework is done in advance, so that I can devote all of my attention towards presenting my poster.

There are a TON of posters at URECA and there are a TON of wandering people; this presents both an opportunity and a challenge. Most people that attend URECA arent there to look at a specific poster; they are just browsing. This means that it is essential to be proactive, and talk to the random people walking by. You dont have to be pushy, but as Becky talked about at the APS convention, you have to meet your audience where they are, not make them travel to you. You never know who you might meet.

If I were to add another lesson to the list I would add:

3. Practice, practice, practice

I had thought about what I was going to say and had practiced my presentation a little, but I hadnt truly prepared. I had only practiced my spiel for a couple of students and by doing so I had only prepared for one audience. URECA tends to attract for a diverse crowd though and I should have prepared for a number of different audiences.

At URECA, you need to be prepared for the lost, dazed, and confused physics majors; the all-knowing professors; the basic knowledge college students; and the students doing research in the same field as yourself. Next time, I am going to think about how to interest each of these distinct groups and get them wanting to learn more about my project.

April 22nd, 2013

Today I did a run-through of my poster to prep for URECA, which is April 24th. We figured out as I presented my poster that my layout for the poster should have been a little different. I should have switched the mathematical model and the types of reflection box; that way albedo and types of reflection would be on the left pane. It would be better this way because these two boxes explain the background physics of the project. Its alright though, you live and you learn. Ill just have to skip around a little when I present my poster on Wednesday.

April 20th, 2013

Day two of the convention was really enjoyable. Dr. James Lloyd started off the talks today with a presentation on Super-Earth and Super-Jupiter. Next was Dr. Zhaolin Lu; his talk focused on graphene, which is only one atomic layer thick and absorbs from 2-3% of white light. Then came Anders Ryd.

Anders talk focused on the search for the Higgs Boson and the LHC. People started dreaming of the LHC in 1983, although it did not become a reality until over 15 years later. Dr. Ryd explained that spontaneous symmetry breaking in gives rise to the mass and spin of the Higgs Boson. CERN is still unsure what the mass and spin of the Higgs Boson is. The LHC has only ever reached of its energy potential and it is currently closed for repairs until 2015.

The most enjoyable part of the weekend for me was getting to interact with the physicists one-on-one. I particularly enjoyed meeting Abby Flowers. She is extremely charismatic, friendly, and passionate about what she does. She works at Philips

April 19th, 2013

Today I had the opportunity to attend the 108th NYS APS Symposium with Dr. Noé. It was a great experience.

The talks started at one with the welcoming remarks. Rebecca Thompson was the first speaker. Her talk was centered on outreach. She had some really good advice for those interested in doing research. Below are some of her main points:

Next was Abby Flowers who discussed decelerations in neonatal hearts. Her research led to the creation of a device that when implemented reduced infant mortality in the HeRo by 20%.

Then came George Lindberg, a graduate student who organizes outreach. His outreach program is called Science Days. They aim to motivate students to pursue STEM fields and promote the interest and enjoyment of science. He said outreach is a very good addition to a graduate students resume. He had some interesting points:

Next was Crystal Bailey. Her talk was entitled Breaking the Myth of the Normal Physicist. She tried to open our eyes to the reality of the non-PhD physicist. Its a common misconception that in order to be successful in physics you have to get your PhD; this however is untrue. It is also untrue that all the good jobs, worthy jobs are in academics. Here is some physics by the numbers and some interesting facts:

The keynote speaker for the convention was Carl Hagan, one of the original Higgs Boson theorists.

God may be subtle, but hes not malicious Einstein

April 15th, 2013

Today we talked about our report and posters more. Dr. Noé suggested we start our reports with a confession on how we got involved in our project. He suggested I look at Marissas report as an example (not super formal).

Dr. Noé sent me Marissas poster as a template. He suggested we dont do categories like abstract, etc., but instead have category names that are more descriptive of the sections content.

Concerning my project results, we measured the current of the laser beam to be 11.2 mA. Divided by 0.4mA/mW (the sensitivity of the photodetector), this is equal to 28mW meaning the laser beam we were using was indeed the 30mW laser. The closest measurement we took for the paper towels were out of whack. This was probably because the paper towels were not completely flat.

April 11th, 2013

We measured the albedo of three good Lambertian surface approximates and one specular surface inside today. We did so by shining a 28 mW HeNe laser at the surface and measuring both the incident and reflected light intensity. To calculate the expected power of the reflected light incident on the photodetector, we used the equation (P/p)(A/r^2). To find the measured power of the reflected light incident on the photodetector, we converted the voltage into current and then divided by the sensitivity factor of the photodetector.

These numbers suggest that the light was completely reflected by the papertowels and the Spectralon. The observed power often exceeds the total power, which cant actually happen, but this discrepancy might be due to uncertainties in the photodetectors measured voltage.

When we reflected the laser beam off the floor we observed a lot of specular reflection. When we reflected the laser beam off the Spectralon we observed very little specular reflection. We observed the reflected light on a piece of white foam board placed directly in front of the beam and to the side. The light was pretty well spread out, although we observed some forward scattering.

Monday, April 8th, 2013

I measured the irradiance of the sun to be 4.3mA today around 1:00 PM. Today is sunny and looks relatively cloud free. Dr. Noe suggested that I take measurements of the suns irradiance as often as possible to see if the irradiance of the sun varies as a function of the time of year.

Friday, April 5th, 2013

We talked more about URECA today. The permission slips and the abstracts are due on April 10th. We looked over some previous titles and Dr. Noe suggested we look at Foos abstract as an example that we should model ours after. Dr. Noe mentioned that both pictures and acknowledgements can be included in our abstract. The dimensions of the research poster will be four feet long by three feet and we will create them from a template using powerpoint.

Thursday, April 4th, 2013

Dr. Noé and I performed another experiment for my project. We recreated the experiment we performed on March 11th. We did these measurements for a dormant grass and green grass. For the green grass, we also did the measurements without the tripod, handheld, to see how accurate this method is because when we took the albedo measurements for snow we did the measurements without the tripod, just handheld. We also took the albedo measurements for grass with a green, blue, and red filter.

We found the albedos to be independent of height yet again. We did not see a significant change taking the albedo measurements with the tripod and by hand.

Monday, April 1st, 2013

Carolyn and Angela have both had some trouble finding projects. In the end, Carolyn decided to do a project doing a consumers reports type thing for light bulbs, testing different properties of different light bulbs ant Angela decided to explore doing a project Claudine patterns.

I was able to help Angela a little with ideas for her Chladni pattern project because I had studied them earlier in the semester when I was considering doing a project on them.

I have been trying to figure out for the past couple of days why we has gotten an impossible result for the albedo of the white paper, I have been trying to figure out how the cosine factor fits in.

Today, Dr. Noé and I did a quick experiment to try and figure this problem out. We shines a laser beam at a white piece of paper and then moved the photodetector around at a constant distance to see if the angle of detection affected the intensity of the reflected light, we found that it did indeed, but not by a factor of cos(theta).

The piece of white paper did not seem as if it was acting as a Lambertian surface, so we tried the experiment again, but reflected the laser beam off a paper towel, which was thicker and had a rougher surface. We found that the intensity of the light was more consistent, but it did still vary as a function of detection angle. Marty Cohen noticed that it looked as if the light was partially passing through the paper towel. We help the paper towel directly in front of the laser beam and sure enough the laser did pass through the paper towel. This means we need another model Lamertian surface.

Experimental issues and possible solutions:

-Need surface that acts as a Lambertian surface +Use fine white powder Dr. Noe has, spectralon, many layers of paper towels compressed -How to compress paper towels +place textbooks on four corners, duct tape to floor or wall very taught. -Need to be able to keep photodetector constant distance from surface measuring. +Attach string to photodetector pull taught -How to attach string to surface measured -Need to measure angle between surface and photodetector +Create large protractor out of foam board -Reflection from protractor. +Paint it black, remove protractor before taking measurements.

Experiments to do:

-Measure albedo of grass, concrete, and blacktop with filters (effectively measure visible light albedo) -Measure albedos of Lambertian surface as a function of height from surface and detection angle.

Friday, March 29th, 2013

Dr. Noe talked to each of us more about our progress today. He created a file entitled project, which has a general outline for my project, a lost of certain graphics, tables and information I should include and a couple of websites. We talked a little more about my abstract. He suggested I break my abstract up into individual sentences and spend sometime paying attention to the wording of my abstract. The abstract deadline has been extended to April 10th for URECA.

After talking to Marty Cohen, Dr. Noe thought that the intensity of the light reflected off a Lambertian surface is dependent on a cosine factor.

Thursday, March 28th, 2013

Today, I had the chance to meet with Dr. Noe outside of class; we discussed my project as well as executed an experiment to detect heartbeat. I showed him the rough draft of my abstract; he suggested that I expand the second paragraph to include all of the experiments we have conducted this far related to albedo.

We shined a red LED through skin and measured the transmission or the reflectance of the light using a photodetector attached to an oscilloscope. We used an amplifier, which you could specify both a maximum and minimum measured frequency for so that all frequencies not falling within this range are not measured thus reducing excess noise. We tried to find a heartbeat for myself unsuccessfully. We tried on Dr. Noes hand and were able to find a heartbeat rather quickly. The signal was fairly consistent: equal periods and amplitudes. I believe that we were unable to find a heartbeat for myself because I have poor circulation. Dr. Noe tried the same experiment later with Foo and they were unable to find her heart beat as well. She also has poor circulation providing support for my hypothesis.

In another experiment (this one specifically for my research project), we shined a laser at a Lambertian surface (a white sheet of paper) and measured the intensity of the reflected light in order to find the surfaces albedo. We measured the albedo at multiple heights and angles. The albedo seemed independent of these factors.

We attached a photodetector, with peak detection in the infrared, to an oscilloscope. We then shined a laser beam at a white sheet of paper, a good approximation for a Lambertian surface, and measured the intensity of the reflected light.

First, we shined the laser pointer directly at the photodetector to determine the intensity of the incident light. We found the current of the direct laser to be 0.48mA. Using the responsivity of the photodetector, 0.35mA/mW, we were able to calculate the power of the laser to be 1.37mW.

Next, we shined the laser pointer at the white sheet of paper with the photodetector attached to the oscilloscope, as shown in the experiment set up diagram, in order to measure the voltage of the laser beam. We chopped the signal by blocking and unblocking the photodetector, so that we were only measuring the changes in voltage and lessened the effect of noise.

We found the voltage of the laser beam to be 0.02v. From our preliminary results, it seems as if the intensity of the reflected light is independent of height from the piece paper and angle of detection. The amplifier was set to a gain off 100.

We calculated the expected power of the laser beam by multiplying the power of the beam by the area of the photodetecter and then divided it by the surface area of the integrating sphere.

The amount of reflected light cannot exceed the amount of incident light; in other words, albedo cannot exceed 1. Our albedo exceeds the maximum albedo by a factor of two therefore it is obviously inaccurate.

The first thing that comes to mind is that the gain on the amplifier may be off. We connected the amplifier directly to the oscilloscope. When the oscilloscope should have read a 2 box difference, it recorded 2.5 and when it should have read 4 it read 5. This means that the gain was inaccurate and was closer to 125, rather than 100. However, this would only change the observed power to 4.56*10^-4mW and the albedo to 1.66, which is still not within the possible range of albedos.

More research needs to be done to calculate the albedos of the white paper, Lambertian surface. We need to better understand the cosine effect.

Friday, March 25th, 2013

Dr. Noe tried to instill a sense of urgency in us today that we need to figure out, start, and write an abstract for our projects. While we were talking about LEDs, Dr. Noe mentioned that our fingers act as filters and transmit red light. Our bodys ability to transmit light in utilized in oximeters. The amount of light transmitted is affected by the the oxygen levels of our blood.

Oximeters

Oxygenated and deoxygenated hemoglobin absorb red and infared light differently. This fact is exploited by pulse oximeters, which shine a red and infrared light through a blood-rich section of the body and then measure the difference in the intensity of the incident and reflected light with a photo sensor. Deoxygenated blood absorbs less light in the infrared and more light in the red, while oxygenated blood absorbs light in just the opposite way.

Its important when in an oximeter to block out all ambient light, as well as remove any high frequency noise and filter out the DC component from the signal. Using an oximeter, it is possible to measure blood oxygen levels and monitor heart rate. The oximeter's photodetector can either be positioned to detect light transmission (through a finger for example) or reflection from skin. The ratio of the detected light signals is proportional to the blood oxygen levels. Monitoring heart rate only requires a single diode, whereas measuring blood oxygen levels requires two. (A normal heart rate is about 60-70 bpm.)

Oximeters rely on photoplethysmography, a non-invasive method of measuring changes in blood volume using a light source. The AC component of the signal encodes the heart rate information meaning the DC component of the signal must be removed.

Friday, March 15th, 2013 - Tenth Meeting

Dr. Noe talked to us about our abstracts for URECA. He explained that a good abstract should be divided into two paragraphs. The first paragraph should speak to the general importance of the project, while the second paragraph should explain what youve done (In this project). Dr. Noe explained that a good title is key. We also met Muse today, a computer science major. She offered to help us with any coding or programming questions we may have.

List of Possible Titles The Physics of Snow The Optics of Snow *Why is Snow So White?* Lambertian Surfaces and Snow The Albedo of Snow and Natural Landscapes The Albedo of Natural Landscapes The Reflectance of Snow An Exploration in Reflectance

Monday, March 11th, 2013 - Nineth Meeting

We talked in more depth about our projects today. Carolyn expressed interest in doing a project on night vision, while Angela was interested in exploring the intersection of optics and acoustics.

We connected an oscilloscope to a microphone today in order to visualize sound waves. We struck a tuning fork and observed the sound wave patterns on the oscilloscope. The wave pattern was roughly a sine wave. We found the period of the sound wave to be approximately four milliseconds, which translates to a frequency of about 250 Hz; the actual frequency of the tuning fork was 256 Hz, so we were pretty accurate.

Dr. Noe challenged Angela to sing in such a way that it would form a sine wave pattern on the oscilloscope. When she sang into the microphone though, the wave pattern of her singing looked like a sine wave with a ton of divots in it. We learned that when the fundamental frequency and its overtones are added together, it creates divots in an otherwise perfect sine wave. We observed that by the beat frequency was displayed on the oscilloscope when two different sources produced sound. Angela and I whistled two different notes and observed the interference.

Research Project

I am still very interested in doing my research project on snow. Below is some information Ive come across in my research.

Impurities in the snow can affect the snows albedo. Understanding albedo is essential in order to predict snowmelt and runoff rates and understanding snowfield growth and decay. In deep snow, grain size affects albedo; in thin snow, grain size, liquid-equivalent factor (the amount of liquid produced by melting), and albedo of the underneath surface all affect the snows albedo. Models for snow albedo should take the change in light absorption with wavelength and the mix of diffuse and direct radiation hitting snows surface in to account, if they want to be accurate.

Grain sizes in snow make the snow more absorptive. The largest effect of grain size is in the infrared, where albedo can fall by a factor of 2+ with a radius change as small as r=50m to 1000m. In contrast, the reduction in albedo in the visible light spectrum is never larger than ten to fifteen percent.

Snow albedo decreases as the liquid-water content increases. This occurs because the index of refraction of water is very close to the index of refraction of ice, as the liquid water replaces the air between the ice grains, it effectively increases the grain size, decreasing the snows albedo.

Why is Snow So Bright?

Snow albedo typically falls between 95% (new snow) and 80% (old snow). Snow is extremely reflective and fresh snow can be approximated by a Lambertian surface. The white of the snow seems whiter against the blue of the sky.

Project

We measured the albedo of natural landscapes as a function of height today. We found the albedo of the diffusely reflecting surfaces to be independent of the height of the photodetector from the ground.

To take these measurements, we hung a photodetector receptor from a tripod at a specific height above the surface we were measuring the albedo of parallel to the surface we were taking measurements for. We then measured the intensity of light reflected off the surface stepping away from the setup so that our shadows would not affect our measurements. We then directed the detector at the sun and recorded the maximum value for light intensity that we measured. This value was equivalent to the direct incident sunlight. We then directed the detector back at the surface we were measuring, stepped away from the detector, and measured the intensity of the reflected light. We repeated this procedure for a height of 100, 80, 50, 20, and 10 cm and for grass, concrete, and a parking lot.

We calculated the albedo of the surfaces by dividing the intensity of the incident light by the intensity of the reflected sunlight. We found the mean albedo of grass to be twenty percent; the mean albedo of concrete to be twenty percent; and the mean albedo of the parking lot to be nine percent. We performed a single measurement for the albedo of dark soil and found its albedo to be seven percent. All of our calculated albedos fell within the range of natural landscape albedos others had reported.

Friday, March 8th, 2013 - Eighth Meeting

We talked about retroreflectors today. Retroreflectors have the ability to reflect light directly back towards the light source over a wide range of angles. We were able to test out a retroreflector during class. No matter what angle you looked at yourself in the retroreflector the image was reflected directly back. The retroreflector we used looked like the cut off corner of a cube. Dr. Noe mentioned a former WISE student, who had done her project on retroreflectors. The retroreflector in her project was comprised of many small transparent high index-of-refraction spheres attached to a highly reflective backing though. This is the same type of reflector used on bikes.

Astronauts on the Apollo missions placed a set of retroreflectors on the moon in order to measure the moon's distance from the Earth. This can be accomplished by shining a laser beam at the retroreflectors and measuring the amount of time it takes for the beam to return.

Dr. Noé showed us two rectangular mirrors attached along their long sides by a hinge. We stood a marker in between the two mirrors and observed its image in the mirrors. The marker was reflected as multiple images. We observed that when the mirrors were positioned at certain angles the reflected images of the marker converge. Dr. Noé explained that the image converges when the angle is equal 180/n, where n is the set of real positive integers.

Why is Snow White

Different colors arise because the electrons within an object vibrate a certain amount in response to energy based on the frequency of the energy. Objects absorb certain frequencies and reflect others. If the particle does not absorb a certain light frequency, the particle can re-emit the photon. The photon will continue to pass through to the next particle. If the light travels all the way through the material, the material will appear clear. In most solid materials, particles reemit most light out of the matrials and the object appears opaque. Ice is not transparent; it is translucent.

Ice is translucent because light photons don't pass through the material in a direct path; the material's particles alters the direction of the light. This occurs because the distance between some atoms are approximately the height of the light wavelengths; this causes the path to be altered and the direction to be changed.

In snow, a bunch of ice crystals arranged together, when a photon enters snow, it is "bounced" around and then reflected out. The same thing happens to all frequencies. All of the visible light frequencies combine to make white. This is why snow is white even though ice crystals are clear.

Friday, March 1st, 2013 - Seventh Meeting

We discussed project ideas and learned some basic Linux programming. Right now, snow/albedo and Chladni patterns are the two topics I am most interested in exploring and possibly doing a project on. I became interested in snow/albedo when we measured the intensity of the direct versus reflected from the snow sunlight. Doing a project related to snow presents a problem because it is already March and the snow will soon be gone. This means that I'll have to be extra creative when thinking up my project. I've been interested in Chladni patterns since I saw a Youtube video about them in tenth grade; my only reservation is that I would really like to do a project which is more directly related to optics, so that I can broaden my scope of knowledge.

Dr. Noé suggested typing *your topic of interest* + demonstration into Google to find project ideas. He also suggested looking at the American Journal of Physics to get inspiration for our projects.

Albedo- ratio of upwelling radiant energy relative to the down-welling irradiance

Fresh snow has a high albedo, typically eighty to ninety percent reflection. It is also the largest single component of the cryosphere, covering an average of 46 million square kilometers or eleven percent of the Earths total surface area annually (Earths total surface area is 510 square kilometers). Snow is responsible for the majority of solar radiation reflection. These factors are a big reason for why snow is a very important part of the global energy budget. In contrast, surfaces such as trees, plants, and soil typically only reflect ten to thirty percent of incident light.

Snow albedo follows a positive feedback mechanism. As snow ages and melts, a percentage of the snow becomes ice. This reduces the snows albedo, increasing the snows solar radiation absorption, which further ages and melts the snow causing a positive feedback mechanism.

Chladni patterns allow us to visualize the nodal lines of vibrating elastic plates. Placing a small particle substance, such as sand, on a vibrating elastic plate, can form Chladni patterns. The particles will be thrown off the moving regions and accumulate at the nodes of the plates. Both the shape of the plate and the frequency of the vibrations influence the pattern that will form.

Monday, February 25th, 2013 - Sixth Meeting

Today, a chemistry graduate student, Yuning, who is currently performing research in the physics department, told us about the work going on in her lab to build an autocorrelator to measure ultrashort pulses, in the pico- and femtosecond timescales. They accomplish this by splitting the beam into two parts and delaying one part with respect to the other. A nonlinear reaction is then used to obtain a signal dependent on the beam's relative time delay and the time delay can be derived from said signal. Since d=vt, we were able to calculate that light would travel 0.3 mm (300 μm) in one picosecond. Figure 1 illustrates the device they are using to measure the duration of the ultrashort pulses.

After Yuning left, we discussed why our results for light intensity when we were outside and the detector was pointed towards the sun, 4.5 mA, varied from the intensity when we aimed the detector at the snow, 1.2mA, from the same height off the ground. The photodetector we had used to take our measurements peaks in detection in the infrared. This would account for why although the amount of visible light coming from both sources seemed comprable the light intensity readings for the two were so dramatically different. Dr. Noé suggested we place a green filter over the photodetector, so that peak detection would occur in the visible light spectrum.

This did not produce the results we expected, there still existed major discrepancies between our readings for the intensity of the direct sunlight and the reflected sunlight. We tried with a red and blue filter as well, but to no avail. A table of values can be found below.

Monday, February 18th, 2013 - Fourth Meeting

Today in the lab, we continued our discussion of polarization and did an experiment involving the intensity of the reflection of light off snow in relation to the height above the snow.

We started the day by checking if the light from a green laser pointer when shined through a sheet of plastic was polarized. We tested this by shining the laser beam on to a whiteboard, placing the plastic sheet in front of the laser beam and then placing a polarizer in between the sheet and the blackboard. If the light was indeed polarized, there should be a ninety-degree angle between extinction and highest intensity. This did in fact occur when the light was shined through the polarizer on to the board.

When we held the polarizer up to our faces though and looked at the laser beam reflected off of the white board, the light did not appear to be polarized. This occurred because the light was diffusely reflected off the white board. Diffuse reflection occurs when light is reflected off a rough surface. The roughness of the surface means that even though the light beams come in parallel to one another and follow the same laws of reflection, they meet surfaces with different orientations; therefore the light scatters in different directions.

There is another type of refection called specular reflection. Light is specularly reflected off of smooth surfaces and in this reflection all of the light is reflected at the same definite angle. We observed this kind of reflection when we reflected the laser beam off of a mirror.

Next, we explored the properties of a sheet of glass, which was transparent when viewed through one side, and was nearly opaque when viewed through the other side. We viewed ourselves through the sheet in a mirror. On one side, it was easy to see yourself, while on the other, our image appeared purple and it was harder to view yourself. We talked about what may be responsible for this. In the end, we determined that the glass was circularly polarized light. We tested whether the light was polarized by shining the green laser beam through the sheet and the polarizer and observing whether or not extinction and full intensity occurred ninety degrees apart. It did occur on one side, but did not on the other.

We then discussed Brewster's angle. Brewster's angle, which is also known as the polarization angle, is the angle at which light that is unpolarized when reflected becomes perfectly polarized. It is also the angle at which light of a certain polarization perfectly transmitted through a transparent dielectric surface with no reflection.

We learned that polarizers can work in more than one way. Some polarizers simply reflect the light at a different angle, while others absorb light in one direction and reflect it in another direction. A number of crystalline materials exist that absorb more light in one direction than another, so that light becomes more polarized as it travels through the material. This kind of absorption is called dichroism. We found out that circularly polarized light changes its handiness when it is reflected, so if it is right-handed it will become left-handed.

We then used a photodetector to measure the intensity of light under different conditions. Sitting under the fluorescent light, we found the intensity of the light to be 0.007mA; standing under the fluorescent light, we measured the intensity of the light to be 0.011mA; when we turned the lights off, we found the intensity of the light was equal to 0.000mA.

We then did an experiment where we measured the intensity of light given off by an incandescent light bulb at different distances from the light bulb. We turned the lights off, so that we were only measuring the light given off by the incandescent bulb. We found that the intensity of the light in relation to distance from the bulb obeyed a power law. A table of values and a graph can be found in my lab notebook. We found that our results were affected by the reflection of light of the ruler.

At the end of class, we went outside and measured the intensity of light reflected off the snow in relation to distance from the snow. We measured the intensity of the sun by pointing the photodetector directly at the sun. We measured the of the sun to be 4.5mA. We then measured the intensity of the sun reflected off the sun by pointing the photodetector at the ground perpendicular to the ground. We found the intensity to be 1.2mA at 80 cm off the ground, 1.3mA at 20 cm off the ground, and 1.4 mA 3 cm off the ground. These values are very close to the same as one another. We hypothesized that the reasoning for this might be that the closer you are to the ground, the more intense the reflected light, but there is a smaller value of angles which will be reflected into the photodetector; whereas the farther you are from the ground, the lesser intensity of the light, but there is a greater value of angles which will be reflected into the photodetector.

Friday, February 15th, 2013 - Third Meeting

Marissa, one of Dr. Noe's former WSE187 students, came in today and talked to us about her WISE project. Her project utilized the small angle theorem to determine the diameter of the sun.

At our last meeting, we had used a mirror that had a cover on it with a small hole made in the center of the cover to reflect sunlight. We observed that as the object the mirror was reflecting the sunlight on to increased in distance from the mirror, the diameter of the reflected light increased. Dr. Noé asked us why we thought this occurred. We originally thought that the light "spread out" as it increased in distance from the mirror because of diffraction. The actual reasoning behind this phonomena is because light rays from different parts of the sun pass through the hole with different directions. The direction that the light ray is traveling in, and the angle between the light rays, is unaffected by the light passing through the hole. The maximum angle between light rays is referred to as the angular size of the sun.

Marissa had utilized the increase in diameter of the reflection with increased distance from the mirror to calculate the angular size of the sun. Her project used both the small angle theorem and s=(theta)r.

The small angle theorem states that for very small angles sin(theta)=x, tan(theta)=x, and cos(theta)=1. When used in conjunction with s=(theta)r, the small angle theorem can be used to calculate the angular size of the sun. This angle is equal to the ratio between the solar diameter and the solar distance.

We had read an article earlier about the 'glitter effect'. In the article, the author proposed that the reason that things 'glitter' is because the angle between the reflected light rays is so small that when the reflected light hits your eye, the diameter of the reflected light is only large enough for one eye to see the reflected light. The fact that only one eye at a time is able to see the light is what causes the glitter effect.

To test this out, we went outside. We each found a glitter from the snow and covered one eye and then the other and observed whether or not the glitter was visible with one eye, but not the other. Using this method, we got mixed results. Some glitters were visible with one eye, but not the other, while some glitters were visible with both eyes. Although the author's hypothesis might be part way true it does not fully explain the glitter effect.

Monday, February 4th, 2013 - Second Meeting

We were able to delve into some optics today. Learning about optics made me realize that I know nothing about optics, but would really like to learn more.

We used holographic diffraction grating glasses to look at incandescent and fluorescent bulbs. The incandescent bulb had a filament and gave off incandescent light, while the fluorescent light bulb utilized gas and phosphors to create its light and gave off white light.

The incandescent light bulb gave off light in a continuum wavelength. Incandescent light bulbs work by thermally exciting atoms via electrical resistive heating. Thermal kinetic energy excites electrons in the solid state. When these electrons drop to a lower energy state, photons are emitted. There is a near-continuum of electron energy levels in a solid, therefore the spectrum of radiation emitted is considered continuous and non-discrete. When we observed the incandescent light bulb through the holographic glasses, a continuum of colors was visible; all the colors gradually blended with one another and there were no discrete bands of colors.

The fluorescent light bulb gave off light in discrete wavelengths; this occurs because in the fluorescent light bulb the light is created when electrons in the gas atoms that are in the excited state drop down to a lower energy level and light is given off. The amount of energy between the two states is discrete; therefore the wavelength of the light that is emitted is also discrete. The light bulbs we were observing were also coated with a phosphor, which fluoresced by absorbing ultraviolet light and emitting it as visible light. When we observed the fluorescent light with the holographic glasses, you could see light was given off at discrete wavelengths because there were solid bands of color and there were no in-between the colors. What I mean by this is if there were red and blue for example, there would be no purple in-between the two; there was no mixing of the colors.

Dr. Noé mentioned lenticular lens in our discussion, but did not go into much depth on the subject. He showed us a bookmark upon which an apple appeared to be falling depending which angle you viewed the bookmark at. After doing some research, I discovered that lenticular lenses are a series of magnifying glasses that are placed in such a manner that different images are magnified when viewed at different angles. This technique is most frequently employed in lenticular printing, which is used to create images that appear to have depth or the ability to change or move. I've seen images bookmarks and posters many times that utilized lenticular lens to make an object appear to move, but I never knew the science behind how they worked.

We talked about polarized light. Light is an electromagnetic wave meaning the wave is composed of both a magnetic and electric field. The magnetic field generally does not interact with matter, while the electric field does. In nonpolarized light, the light wave vibrates in more than one plane; in polarized light, the vibrations occur in a single plane. Light can be polarized circularly, linearly, or elliptically. Light is most often polarized elliptically. One way to polarize light, and a method that we employed is polarization through the use of a polaroid filter. In this method, a material that is capable of blocking some of the planes of vibration of the light wave. Only vibrations that are parallel to the polarization axis are able to pass through and vibrations that are perpendicular to the polarization axis are blocked.

We discussed that polarized light is a vector it has both a magnitude and a direction. Scalar light occurs when light only has a magnitude. We also discussed wave fronts in relation to light. A wave front is a point on a wave that moves with time as the wave propagates. Rays can be drawn to visually represent the path of light. The rays should be drawn perpendicular to the the wave fronts.

I have been looking around me for inspiration for my research project, but have yet to find something. I found that my friend's older brother is going to be studying quantum optics in graduate school; maybe I could connect with him and see if he has any suggestions.

Friday, February 1st, 2013 - First Meeting

We met as a group for the first time today. Dr. Noé introduced me to Angela and Carolyn, two WISE students, who will also be doing research in the lab this semester. Right now, we are scheduled to meet on Mondays and Fridays from 1:00 until 2:20. Dr. Noé spent the first meeting explaining to us what he expected from us and what we could expect from this experience.

Dr.Noé explained that we would all be given a lab notebook and would have a webpage for us to keep a running log of our research projects and our experience in the LTC. The lab notebooks should be done in pen and include relevant diagrams that illustrate the concepts we are studying. He showed us a few example journals. They were all very neatly written and included a number of diagrams. He stressed that journals should be done as neatly as possible. Dr. Noé also explained that we would each be creating a website with a bio, journal, and report. I'm really excited to try my hand at programming.

The possibilities for a research project are nearly endless, as long as they still pertain to optics. Dr. Noé told us about one student, Jill, who did research on the properties of glow-in-the-dark stars; there was another student, Marissa, who calculated the angular size of the sun for her project; and yet another, Sriya, who calculated the properties of the "Mirage Toy" Dr. Noé had showed us. There is wide range of options for our projects. Dr. Noé encouraged us to critically observe the world around us in order to find inspiration for our optics projects.