Marissa's+Telescope+Lab

=Telescope Lab= March 26, 2010


 * Participant**: Marissa Marton


 * Purpose**:

The purpose of this lab is to build a telescope in order to gain a better understanding of light refraction through different types of lenses. In doing this, an image can be created of a specific object. We built a telescope in order to observe the light waves and how magnification works.


 * Brief Description of Experiment**:

Prior to the experiment, the class conducted multiple drawings that involved measurements and calculations in order to understand how light rays are refracted when they penetrate unique lens types. This deepened our understanding of refraction and made it more beneficial for when we went to build our telescope. In building the telescope, we first had to place a lens on a yard stick and use the light that came through the back window to find the focal length of the lens. We did this by obtaining an index card and mounted it to the yard stick so that we could move it and determine the focal length (from left to right: index card, lens, window). As a result, the outside image that came through the window was projected onto the card and we were then able to move the card and take a measurement of where the image was in the optimum focus. After doing this, we added a second lens and determined that it was the distance of the sum of two focal lengths. When we looked through one lens and into the other, we could see a nice, magnified image; however, the image was flipped upside down. As a result, we knew that we had to add a third lens to our telescope and we also discovered that we had to block out any outside light because this will affect the image in a negative way (light coming in would contribute to the image being upside down). We then decided to make a tube out of rolled up poster board in order to block out the light, which would alter the image that we were trying to achieve. By creating this tube, we were able to see a nice, but not terribly sharp, magnified image that was right side up in the end. We learned from this trial and error process that the first lens flips the image upside down, the second image flips the image right side up, and the third image magnifies it.


 * Data**:

Below are some interesting pictures of the telescope (made by Hannah and Marissa) and some pictures of a drawn out diagram of the telescope lenses, focal points, and rays (drawn by Marissa):



(Left to Right)

1: Picture of the telescope on the yard stick with the three lenses and a tube being supported. 2: Picture of the telescope and just beyond it is the light source that we were focusing on in order to see if we had proper magnification and if your image was right side up. One can also see a sheet of paper in the center of the skull picture on that banner. We were able to support our telescope with books (see image 1) in order to angle it correctly to see a magnified image of what was on the sheet of paper. 3: Picture of our magnified image on a sheet of paper stuck up on the wall in the middle of the skull picture on a banner (see image 2).



This is an image of a diagram of the telescope lenses, focal points, and rays (as well as the object on the far right). This diagram had to be scaled down 25% in relation to the actual telescope in order to draw it on the poster board.



(Left to Right)

1: Close up of two of the three lenses and rays. 2: Close up of all three lenses and rays.

In this diagram, the rays meet (shown just under the focal length to the left of the lens) in an odd location because the object here in the diagram was drawn at a distance of three focul lenghts away. However, with our actual telescope, the object was much further away. As a result, our image does not appear how it normally would on a diagram involving this type of refraction. The first arrow on the right (in image 1), is where the image will appear flipped upside down. Where the rays intersect at the farthest arrow to the left, the image will become flipped right side up. Finally, the middle arrow (seen in lens 2) is where the image will appear magnified.


 * Sample Calculations:**

Calculation// || Focal Length (cm) = Calculation// || Magnification = focal length of objective lens **÷** focal length of eyepiece ||
 * //Focal Length (cm)
 * [**Object Distance (cm) **x** Image Distance (cm)**]** **÷** **[**Object Distance (cm) + Image Distance (cm)**]** ||
 * //Magnification

We were able to successfully construct a telescope that magnified an image of an object that was an infinite distance away. In doing this, we learned that the lenses create a magnified image by working together. The first lens flips the image upside down. The second lens flips it right side up, and third image magnifies the image. Overall, it was a very beneficial experience and helped us to learn how a telescope works and how rays are refracted.
 * Results**:


 * Lab Questions**:

1. Choose your favorite combination of lenses for the telescope and describe its properties. Our fevorite combination of lenses for the telescope was the objective lens with a focus of 47.1 cm and an eyepeice of a focus of 9.7 cm. These two lenses were placed at a distnace of 51.4 cm apart. The magnification of the lenses was calculated by dividing the focal length of the objective lens by the focal length of the eyepiece. For our magnification of these two lenses, it was 4.299.

The graph below depicts the use of various types of lenses (e.g. curved lens, one sided curved lens, single convex, and small / large curved lenses). It is looking at the magnification in relation to the various lens focal points. We can see here that as the focal length decreases, the magnification increases. Also, the lens described above is depicted in this graph (magnification of 4.299 with a focus of 51.4).



I do think that our experiment produced a valid and reproducible result because we were able to see first hand how a telescope is successfully constructed and how all the components work together. In addition to this, the lenses that we used had specific focal lengths and this also allowed for a reproducible experiment since the focal length won’t differ. In other words, our telescope construction or structure was easily reproducible. An improvement to the experiment could consist of going over measurements to make sure that they are as accurate as possible or securing our lenses to the yard stick better in case of any shifting (which would cause for an alteration in the correct focal points). Another thing that could have potentially helped us more would have been to use something more idea to block out the light rather than poster board. We did have a gap in certain places because the poster board was not long enough. We could have even used one tube and cut a slit in it for the second lens. Blocking out as much light as possible would have been best in creating a sharper image.
 * Conclusion**: