Monday, March 1, 2010 ^÷ Finishing up
† Today Dr. Noe and I double-checked the effects of the green laser on an inactivated star.† Last Friday we had wrapped the glow-in-the-dark materials in a black cloth and put them in a desk draw in order to completely `kill' their glow.† Today we removed and uncovered the stars in an unlit room, and then exposed them to the green laser again.† The stars glowed very dimly, but the green laser definitely activated them.† Besides going over experiments, I worked on typing up my report and working with my web page.† Also, I began to take readings of the decay of one star.† We are going to compare this data with the data that a previous student named Jill made.†
Today was my last day working in the Laser Teaching Center.† I feel that benefitted from working with Dr. Noe and his inactive demonstrations of physics, and I am very grateful for everything he has taught me. †††††
Friday, February 26, 2010 : Glow-in-the-Dark Stars
Today Dr. Noe and I experimented with glow-in-the-darks materials.† First we used a green laser pointer to determine its effect on an inactivated star.† We observed that this light source did not cause the star to glow.†(Later on we did see a very slight effect.) I explained to Dr. Noe that when I was about twelve years old I had used a black lamp to enhance the glow of my glow-in-the-dark stars.† We then used the black (ultraviolet) lamp in the LTC to demonstrate this.† The stars fluoresced while being exposed to the UV lamp, and when they were removed from the light source, they initially glowed very brightly.† We experimented with all the light sources available in the LTC.† Most of the light sources activated the stars, but the red HeNe laser did not.† We performed another experiment using the stars when they were already activated to see whether light sources would deactivate or bleach the stars' glow.† We found that both the HeNe laser and the green laser pointer bleached activated stars.† I really enjoyed experimenting with the glow-in-the-dark materials and witnessing their reactions to different light sources.† †††††††
Thursday, February 23, 2010 : Nergis Mavalvala
Today we met Nergis Mavalvala, a professor at MIT. Nergis is very enthusiastic about lasers.† Dr. Noe showed her the different lasers available in the Laser Teaching Center, and during her tour she noticed the Mirage toy.† I attempted to explain how it works, but I needed Dr. Noe's help to finish the explanation.†
Nergis is involved with the Laser Interferometer Gravitational Wave Observatory (LIGO) and she gave a talk titled `Laser Interferometer Gravitational Wave Detectors: the search for the elusive wave.' She began with simple concepts and ideas.† Some familiar terms she mentioned were supernovas, neutron stars, and black holes.† According to Nergis's presentation, these are some of the astrophysical sources of gravitational waves.† I enjoy astronomy and astrophysics so I found that part of the talk very interesting and exciting.† I understood most of what she spoke about in the first ten to fifteen minutes, but after that I was completely lost.† I became confused when she explained how LIGO tries to detect the gravitational waves.† Overall, it was still a great experience to meet and speak with Nergis.† ††
Thursday, February 18, 2010 : Focal Length and Image Creation
Today was very interesting. When Jackie and I entered the Laser Teaching Center we were surprised to find several people in the lab. The first person we met was a graduate student named Meredith. She had finished her undergraduate education double majoring in physics and chemistry. She is currently interested in studying material science. Meredith was contacting Dr. Noe about working on a project in the LTC.
After our conversation with Meredith, we noticed that there were other visitors in the lab. Dr. Noe was speaking to a high school student and his father about working in the LTC over the summer. Dr. Noe decided to take everyone outside to experiment with different lenses and the sun. We had been waiting to use the different lenses outside for weeks, but the weather had kept us for doing so.† While we were outside, we found the focal length of different types of lenses.†† The large spherical lenses had a very short focal length while Dr. Noe's glasses had a much larger focal length. Dr. Noe had a lens that was so slightly curved that it seemed as if it was flat. He said that this lens had a focal length of about 3 meters. I found the focal length of a magnifying glass. I was able to see a clear inverted image of the sun in the sky. Once the focal length was found, we used the magnifying glass to burn black paper. Also we spoke about the small angle approximation again.
When we were done and cold, we went back to the LTC.† The visitors noticed the Mirage toy and Dr. Noe explained how it worked.† Since we had spent time understanding this toy in the beginning of the semester I was able to help explain how it worked.† After this, we revisited a question that Jackie had asked during our last session.† On Tuesday we were using lens to create images of a light bulb on the white board.†† When Jackie used the magnifying glass, she found the focal length, and an inverted real image appeared on the white board.† She asked Dr. Noe how she could make the image upright.† We spent the rest of our session today trying to answer this question mathematically by manipulating equations.† When the answer was revealed, Jackie was able to demonstrate it with lenses.†
Tuesday, February 16, 2010 - Small Angle Approximation & Lenses
Today Dr. Noe began by reading through our last journal entries, and critiquing our individual writing styles.† In Jackie's journal, she asked Dr. Noe to review a few topics that were complicated and confusing.†
Then Dr. Noe went over the small angle approximation.† By using the unit circle, we were able to derive an equation and visualize how it works.† Astronomers use this method to determine the size of distant celestial bodies.† We used the equation for a different purpose.† We looked up the diameter of the moon and the moon's distance from the Earth, and we calculated the angle.† We found it to be 0.01 radians.† Solar eclipses are possible because the sun and the moon are the same angular size when seen from the earth.† Only the Earth's moon displays this phenomenon.† Dr. Noe also demonstrated how he used the small angle approximation to estimate the length of a ballroom as about 300 feet.†The discussion on the small angle approximation led to an explanation of dimensionless numbers.† Some examples include pi, degrees, and ratios.† Dimensionless numbers are also known as pure numbers.
Next Dr. Noe reviewed properties of lenses.† He drew ray diagrams for a converging lens.† Using the pictures, he indicated where the distance of the object and the distance of the image were.† Most high school physics teacher draw the ray diagram with only two rays.† Newton used many parallel rays of light in his ray diagrams, and Dr. Noe felt that this was a better representation of the diagram.††† After drawing the diagrams, he explained focal length and how to calculate it.† In the case of the sun, the focal length is equal to its image distance.†
Lastly, Dr. Noe mentioned that the sun is not a point.† Rays coming from different parts of the sun will hit the Earth at different angles.† I was surprised when Dr. Noe mentioned that it is more dangerous to look into a laser beam than to look into the sun.† We found that the laser beam and the sun have the same power per area.† The quality that makes the laser more dangerous is that the laser^“s light diverges by a lot (about a factor of 10) less than the sun. ††
Dr. Noe discussed possible projects I could do using glow-in-the-dark stars.† I could experiment with different wavelengths of light and see how they affect the glow of the stars.† He contacted a store to purchase stars.† I am very excited to experiment with them.
Thursday, February 11, 2010 - Microscopy
Today Dr. Noe tried to focus on possible projects for Jackie.† He began by providing a brief history of microscopy.† Before microscopy, Galileo used lens to make a telescope with which he was able to observe the moons of Jupiter and other celestial bodies.† Other early optical devices included reading glasses and spectacles.† Antom Von Leeuenhoek was the first person to use lens to magnify.† He specifically used the lens to look at the details of fabric.† Later he began to use the lens to look at blood and dirty water, and he saw microscopic animals.† Leeuenhoek is referred to as the founder of microbiology.† Dr. Noe suggested that Jackie could make a simple microscope as her project for this rotation.† He also provided more specific information about the properties and use of lens.† This led to discussions about focal length, lens shapes, and indices of refraction.† †
Next, Dr. Noe returned to his discussion of light.† He explained that there are many theories of light.† The scalar theory of light explains Young^“s experiment and interference patterns.† The simplest way to think of light is to think of it as rays of light.† The ray shows the direction of the light.† The wave theory is more complicated but it is useful for more detailed aspects of light.† After introducing the theories of light, Dr. Noe began to talk about angles, degrees, and radians.† He asked questions such as, "What units are angles measured in?" and "What are radians?" and "Why are there 360 degrees in a circle?"† The answer that surprised me the most was that the 360 is an arbitrary number used originally by the Babylonians.† This group of people had created a number system based on the number 60.† The 360 degrees in a circle may have been related to the days in the year.†
Toward the end of the period, Dr. Noe concentrated on my interests.† He showed me projects regarding polarized light.†† I was particularly amazed by the artwork of Jess Newman.† She used cellophane and polarized light to make beautiful pictures that would change colors when the pictures were rotated.
Tuesday, February 9, 2010 - Light and Possible Projects
Today we returned to our discussion of the images created by the Mirage.† Dr. Noe reiterated that the images of the pigs are real images because light rays actually converge at the image location (Physics Classroom).† This allows the projection of the real images on a screen.† Dr. Noe demonstrated this by replacing the two plastic pigs already in the Mirage with a quarter.† He scavenged the lab until he found a small translucent disk.† When the disk was held very close to the image of the quarter and then tilted at an angle, the image appeared clearly through the disk.† When Dr. Noe moved the disk slightly away from the optimal position, the image of the quarter lost focus.† This also occurred when the disk was held directly over the image.†
After the demonstration, Dr. Noe spoke about light in general.† First, he asked us questions to see how much we had retained from our study of physics in high school.† When I mentioned light having wave and particle properties, he said that light was not a stream of photons.† He said that light acts as a particle when it comes into contact with matter.† After making this point very clear, Dr. Noe began to explain why light is referred to as a transverse electromagnetic wave.† Before he explained he asked, "What is a field?" I had remembered studying fields in physics but I was unable to verbally explain what it was.† After Dr. Noe explained fields, it was easy to understand light as an electromagnetic wave.† Light has electric and magnetic fields that travel perpendicular to one another.† Next, we discussed the electromagnetic spectrum.† This conversation led to tangents about units, sympathetic vibration, and octaves.† Lastly, Dr. Noe showed us an interference pattern of a red laser.† †The laser beam passed through and bounced off a series of lens and mirrors until an interference pattern was created on an adjacent wall.† Dr. Noe used a torch to show how heat changed the index of refraction of air and affected the interference pattern. ††††††††
Throughout our time in the lab, Dr. Noe tried to think of possible projects for us. I became very excited when he spoke about fluorescence. We discussed previous projects using glow-in-the-dark stars and possible projects for my rotation.
Thursday, February 4, 2010 - Laser Teaching Center & Dr. Noe
Today was our first official meeting with Dr. Noe.† He showed me and Jackie around the Laser Teaching Center, and he explained his expectations for our rotation.
After the introductions, Dr. Noe showed us the Mirage Pigs.† It looked like a flying saucer with a circular opening on the top.† This instrument uses parabolic mirrors rather than spherical mirrors to create an image of two pigs over the circular opening.† At first, we thought that the image was virtual, but this was disproven through a series of experiments.† First, we used a magnifying glass and determined that the image could be magnified.† Then, we used a laser pointed to see whether the image would light up, and they did at certain elevated angles.† †Finally, Dr. Noe explained that the imaged created by the Mirage was a real image.† I drew a diagram of the mirrors to show how the rays of light were being reflected to create the image of the pigs.† The parabolic mirrors do this by reflecting all the light at one point.† This causes the image to be real, inverted, and magnified