Research Journal

Tuesday, February 23, 2010

Today we met a successful woman in science: Prof. Nergis Mavalvala from MIT. Prof. Mavalvala presented her work on the Laser Interferometric Gravitational Wave Observatory (LIGO) project at the physics department colloquium that coincided with our final official meeting of this rotation. She subtitled her talk ``the search for the elusive wave'' since gravitational waves are very difficult to detect -- in fact no one has yet done so.

We met with Nergis†in the laser lab before her talk. Dr. Noe gave her a tour around the lab and explained some past projects. This led to a discussion of what Ashley and I have done during our rotation. It was a great experience to talk with such an intelligent woman and discuss our projects with her. Though our projects are extremely simplistic compared to her work, I believe Nergis appreciated hearing about the start of our research experiences.

Nergis' presentation gave me an impression of how complex and difficult her research is. I did appreciate that she began simply, by defining terms and outlining the basic ideas behind LIGO and her research. From this point she gradually went into more and more complex concepts and results. Dr. Noe described the path of the presentation as ``spiraling into a black hole.''

It was interesting to attend this colloquium and Dr. Noe was right when he said that undergraduates should take advantage of opportunities such as this. Hopefully there will be presentations such as this that better suit my interests.

Thursday, February 18, 2010

We had guests in lab today. When class began, Dr. Noe was giving them a tour of the lab and showing them some of the experiments that Dr. Noe had shown me and Ashley. It was fun to see the expressions on their faces when conducting some of these activities, especially the pig "mirages." Ashley and I must have had the same expressions when we did the activities for the first time.

With the guests watching, we moved onto continuing our discussion of lenses. Last Tuesday, we conducted an experiment to understand the relationship among the focal point, distance of an object and its image. We found that we could make an image, but the image was inverted. I then asked if the image could be again inverted so that it appears to no longer be inverted. Today we were able to do this. In class, we derived a formula that would help us place the lenses in the correct position. This was derived by using the 1/f = 1/do + 1/di and plugging it into a quadratic equation.

This activity was another step to determining my project. I agreed with Dr. Noe that a more realistic project that can be completed in the time allotted will be understanding inverted images.†

Tuesday, February 16, 2010

I especially enjoyed today's topics in the laser lab. Dr. Noe discussed how he applied the small angle approximation at an event he attended. He wanted to find the distance of the room by approximating the angular size of a person across the room. Comparing the angle to the diameter of the moon, found the angle. He approximated the height of the person. With this information he used the tangent function and took the height and divided it by the angle and found the distance of the room. Through this example, I better understood the lesson of small angle approximation he started last week.

We then discussed the physics behind lenses to strengthen my project on microscopy. We discussed how converging lenses function. The curve in the lens allows light being shined parallel towards the lens to come together at one point, creating an image of an object. With a diagram, Dr. Noe displayed why and how the light bends.

I helped conducted a display of how a lens works by holding a lens in front of a lamp and creating an inverted image on the opposite wall. It was amazing to see how clear the image appeared on the opposite wall. If I moved it even closer to the wall, I created an even smaller and clearer image. This is because there are two focal points between the light object and wall. I then asked, "if there were two lenses between the object and the wall, would the image not be inverted anymore?" So we tried it. If I put the lenses closer, the image was just magnified even more, but if there was space between the lenses, it created an image.

There was not enough time to conduct the rest of the experiment. Dr. Noe instead had me figure out a formula to find the distance of the image if two lenses were used.

Thursday, February 11, 2010

In this week's lab, I confirmed with Dr. Noe on a project for me to work on. I will be doing a project on microscopy which will hopefully lead me to construct my own simple microscope. I chose to do this ????

Since I decided this, he began to discuss the history of microscopy which later lead to a discussion on the physics behind microscopy.

Anton van Leeuenhoek discovered the microscope in the 1600s [not true] where he magnified threads to look at textiles. It was later used to look at microscopic items such as blood and seamen. At a time where cells were not yet discovered, the microscope became a blessing for scientists.

The index of refraction of an object describes how light slows down going through an† object (NA = nsinx). This is important in microscopes because it uses a lens to magnify. The light goes through the air to the lens making the light bend which allows the picture to be magnified.†

Researching more about simple microscopes, I came across a website that says how to make a microscope with a drop of water. If I were to study why this method can make a microscope, I may be able to make my own.

I would like to go over focal lengths again and how important they are to view an image. Does a simple microscope require more than one lens? diameter of the moon = 3†474.8 kilometers Distance from Earth to Moon = 384,403 km Pasted from A table-top model can also be constructed, which is a little easier to use for small specimens. Cut a strip of metal about 4 inches by 1 inch (100mm x 25mm) from a metal food can or from sheet stock about the same thickness. File the edges if they are jagged or sharp. Place the metal strip on a piece of wood, and mark the exact center. Drill or punch a hole app. 1/16-inch (1.5mm) through this center mark. However you make this hole, keep in mind that it should be as round as possible, and that it should be clean and free from burs. The metal should not "pucker" around the hole, which can happen if it is punched. It is a good idea to polish around the hole with light grit paper to clean it up. Blow out any dust that remains afterwards. [clip_image001.gif] Bend the ends of the strip down to form a stand. Oil or grease around the hole as above, and, using a pencil, transfer a drop of water to the hole so that the drop remains in the hole. Place a small sheet of window glass on top of two cans, which are set at either end of the glass. Carefully place the metal strip on the center of the window glass, being careful not to dislodge the water drop "lens". Prop a small mirror under the glass so that light is reflected from it and up through the lens. Place whatever it is you want to examine beneath the lens (pollen, small insects, grains of salt or sand, etc.). Focus by gently pressing on the strip. Pasted from [clip_image002.png] ---------------------------------------------------------------------------

Tuesday, February 9, 2010

Today we went over many topics during our time in the lab. We discussed the properties of light and waves, which lead to discussion of potential projects to pursue this rotation. Dr. Noe defined what a field is and how light travels through a field. He explained what determines the path of light. The light is moved by a force (F = qE).

We also discussed that light can be considered as matter when it comes in contact with an object. Dr. Noe emphasized not to think of light as a beam of photon particles. This is not what light is.

We then discussed the equation (lambda)(frequency) = (speed of light)/(index of refraction). With this equation, the speed of light can be determined.

We talked a lot about units and the importance of knowing them in the lab. Measurements the a power show the enormity or microscopic size of something. It is better saying 1000mm than 1x10^3mm to emphasize how large it is. It was interesting to know that they had names for units up to 10^24 power.

What interested me was how glow in the dark stars are illuminated better in certain lights. In fluorescent lights rather than incandescent lights, the stars glow better. This has to do with the light intensity the fluorescent light emits.

By the end of the class, we looked at an experiment someone conducted in the lab that involved a light that was intensified through a lens and shined into a cube. Due to the index of refraction of the cube, the light split into many different directions. The light was captured in many different mirrors placed all over. The mirrors then came together at one point on the wall.

A topic that I thought was interesting was the topic of microscopy. I hope to further study this in the lab and possibly do a project on it.

Thursday, Feb. 4th, 2010

Today was my first day in the Laser Lab with Dr. John Noe. Right away, we conducted our first experiments. Though they were small and simple, it was a stepping stone into experiments that I will be conducting in the lab throughout my rotation.

Dr. Noe brought out the "Mirage" pig and encouraged me and my lab partner to try to touch the two pigs that appeared to be standing on a container with a hole in the middle. The pigs looked as if they were sitting right on top of the container, but when I attempted to touch them, I realized that they were images. We later found that the pigs were not sitting on top of the container, but were placed inside the container. They also appeared bigger and standing facing us instead of away from us (like we positioned them inside the container). When Dr. Noe asked to describe the pigs, I answered with an unclear answer that the pigs were not real images. The word ^”real image^‘ struck a nerve with Dr. Noe and the three of us began to delve into the description of a ^”real image.^‘ Giving us a magnifying glass, Dr. Noe asked if the pigs could be magnified. I was able to magnify the pigs and was now skeptical with my previous answer. We further tested the word "image" by attempting to shine a green laser beam on the pigs. At a certain angle, the beam hit the pigs in one spot. But when the beam was shined perpendicular to the pigs, the beam did not hit. Beginning to ponder why the beam did this, we realized it involved the mirrors inside the container and the curvature of the container itself. Due to the law of reflection when the beam is held at an angle, the mirrors reflect the rays many times in angles perpendicular to the surface of the mirror. The orbital curvature of the container allows the path to reflect in many different directions till it reaches the hole of the container. When the path of the beam reaches the hole, it seemed as if the beam was hitting directly at the pig. We then realized that the light beams of the room reach the pigs and reflect the image of the pigs inside the container out to the top.

This causes the "mirage."

A real image a representation of an object in which the perceived location is actually a point of convergence of the rays of light that make up the image. Below shows how the image is reflected. The pigs follow a similar path to show real images above the container. [clip_image001.png]

A question that I have for this experiment is why the pigs are facing towards us while we placed them in a position away from us.

This was an interesting and fun way to start off the lab.