#$&*
course PHY 202
1 hr
Experiment 29: InterferenceUsing 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.
According to your results, how is the spacing between the bright spots on the wall related to the distance between the lines?
I stood 16-ft away from a closed door down the hallway with all the lights out with a laser pointer and the piece of diffraction grating transparency. I shined the laser through the V near the top of the pattern and observed and image that appeared to have a distinct red dot in the middle with several dots appearing almost sprinkled across the door with a few straight lines shooting out in different directions. As I moved the laser pointer down the V shape I noticed that the straight line shooting out would move around in different directions, almost rotating around the center dot as the laser moved down it.
The vertical position of the beam on the V is located near the bottom of the V pattern.
It would appear the the average distance between the distant bright spots formed on the wall would be ROUGHLY 1 to 2 cm apart. The spacing is smaller near the center and gradually gets larger the further away form the center dot. I only see one big right distinct spot with several smaller spots all around the center dot. The width of the V at the point where the beam is pointing through is .4 cm. Just one space between the threads across this width.
I used the rectangular shapes and repeated the test. I saw the most significant diffraction on the roughly 2.5 cm x 2.5 cm square with the most number of horizontal and vertical lines. The spacings were tighter between the center dot and all the other dots. It appears that the tighter the line spacing the smaller the distance between dots.
"
Self-critique (if necessary):
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Self-critique rating:
#$&*
course PHY 202
1 hr
Experiment 29: InterferenceUsing 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.
According to your results, how is the spacing between the bright spots on the wall related to the distance between the lines?
I stood 16-ft away from a closed door down the hallway with all the lights out with a laser pointer and the piece of diffraction grating transparency. I shined the laser through the V near the top of the pattern and observed and image that appeared to have a distinct red dot in the middle with several dots appearing almost sprinkled across the door with a few straight lines shooting out in different directions. As I moved the laser pointer down the V shape I noticed that the straight line shooting out would move around in different directions, almost rotating around the center dot as the laser moved down it.
The vertical position of the beam on the V is located near the bottom of the V pattern.
It would appear the the average distance between the distant bright spots formed on the wall would be ROUGHLY 1 to 2 cm apart. The spacing is smaller near the center and gradually gets larger the further away form the center dot. I only see one big right distinct spot with several smaller spots all around the center dot. The width of the V at the point where the beam is pointing through is .4 cm. Just one space between the threads across this width.
I used the rectangular shapes and repeated the test. I saw the most significant diffraction on the roughly 2.5 cm x 2.5 cm square with the most number of horizontal and vertical lines. The spacings were tighter between the center dot and all the other dots. It appears that the tighter the line spacing the smaller the distance between dots.
"
Self-critique (if necessary):
------------------------------------------------
Self-critique rating:
#*&!
&#Your work on this lab exercise looks good. Let me know if you have any questions. &#