#$&*
course phy 122
Professor,I have to admit that this was about the most frustrating experiment that I have done so far. HAHA. I think that I need to start wearing the lenses that I used in our previous assignment in order to complete this one. I had a hard time seeing the numbers on the ruler that I hung on the wall. I hope you have a good evening. I am going to complete Test # 2 in the morning. I will send you a notification once I have finished it.
Submitted 3/17 8" "Experiment 29: Interference
Using a hand-held laser pointer and a diffraction grating consisting of lines on a rectangular transparency, we observe the maxima created when the light is directed through the pattern at various separations, and with various incident angles. We determine the angular separation of the maxima and use this separation to estimate the wavelength of the light. We then use sets of parallel straight lines on the same transparency to determine the wavelength of the light.
Stapled to the paper rulers in your lab materials package is a rectangular transparency a few inches on a side. The transparency contains copies of various patterns of lines.
In at least one pattern the lines form a V.
Orient the pattern so that the V is upright, with the widest spacing at the top.
Move at least 3 and preferably 5 or more meters from a smooth wall. Shine the laser through the V near the top of the pattern and observe the image made by the light on the wall. Measure the distance from the transparency to the wall.
Gradually move the laser down through the V, so that it shines between lines that move progressively closer and closer together. Observe what happens to the pattern on the wall.
Continue moving down the V until you obtain the most distinct possible set of bright spots on the wall.
Note the vertical position of the beam on the V.
As best you can, determine for this position the average distance between the distinct bright spots formed on the wall.
Measure the width of the V at this point, and the number of spaces between the threads across the width.
Record also the distance to the wall.
There are also a few rectangular patterns consisting of parallel lines. The spacing of the lines varies from rectangle to rectangle.
Repeat the preceding exercise using different rectangular grids.
For each grid determine the average distance between the bright spots on the wall, the average distance between the grid lines and the distance from the plastic rectangle to the wall.
Information for V pattern obtained:
When I performed the experiment for the V pattern, I noticed that the dot reflected onto the wall through the plastic transparency was higher in position than I was holding it in front of me. I had difficulty holding the laser and the transparency still while performing the experiment. After obtaining the general height on the wall, I managed to fasten a yardstick horizontally on the wall to complete the measurements. The transparency was placed about 120 inches from the wall. I must repeat that I had minimal difficulty holding steady for the experiment and the following measurements are probably not very accurate. The bright spot on the wall measured approximately 70 inches in height vertically. When I traced the spaces between the lines, the same shape was transcribed onto the wall that was on the transparency only larger and more spaced out. The width of the V was about 20 inches and the space between the lines was approximately 1.5 to 2 inches depending on the distance of spacing on the transparency. If the space was larger on the transparency, then the increment of spacing was greater on the ruler. As stated previously, all of my measurements were approximate. It would be very difficult to demonstrate precision with this experiment without a controlled environment.
Information for rectangle patterns obtained:
As stated on the previous experiment, it was difficult to remain stable for measurements. All of the following measurements are approximate. When I measured the rectangles, I used the same distance from the wall to the transparency of 120 inches. The vertical height on the wall was 63 inches ( I sat down for this experiment). In the first rectangle I measured the width was 20 inches, with the increments in spacing about 1.5 to 2 inches (Pretty close to the experiment with the V) The second rectangle was very similar to the first. The last rectangle I measured had closer lines and the lines were an inch or less apart when reflected onto the wall. The interesting anomaly about both experiments is the fact that the light from the laser reflects upward with the V and with the rectangle when passed through a transparency.
According to your results, how is the spacing between the bright spots on the wall related to the distance between the lines?
The greater the distance on the transparency between lines, the greater the distance between the lines on the wall, the lesser the distance between lines on the transparency, the lesser the distance between the lines on the wall.
What is the ratio of the spacing between the dots to the distance between the plastic rectangle and the wall?
The distance between the lines on the transparency are about .10 of a cm, and the distance between the reflected dot on the wall was about 1.5 inches.
What distance is in the same ratio with the spacing between the lines?
Im really not sure what you are asking here, Professor. If you will clarify, I will be glad to answer the question.
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&#Your work on this lab exercise is good. Let me know if you have questions. &#