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course Phy 202
3-24-14 light lab
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course Phy 202
Part AA panel light is 170cm above the surface of a table. We used four different size lenses held parallel to the surface of the table to focus the image of the light onto the surface of the table and moved up or down to better focus the image.
We then measured the distance from the table to the lens when focused and recorded the size of the image produced on the table top.
First column is distance from table top, second column is image size
6.5cm 2.5cmx5.5cm
5cm 3.0cmx7.2cm
3.75cm 5.5cmx11cm
4cm 1.6cmx3.0cm
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Data I received from other students indicates that the further the lens from the tabletop, the larger the image. It seems we also saw that prior to running the experiment.
This doesn't seem to be the case with your data.
Are you sure of your data?
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Assuming your data, what are the focal lengths of the lenses? I believe everyone agreed that the focal lengths were roughly 7, 10 and 14 cm.
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I reported the wrong measurement from table top, I accidentally reported lense size.
First column distance from table top, second column distance object to lens, third measurement is image size fourth column is focal lengths.
5cm 165.0cm 1.6cmx3cm 4.85cm
7.5cm 162.5cm 2.5x5.5cm 7.19cm
9.6cm 160.4cm 3.0cmx7.2cm 9.07cm
15.2cm 154.8cm 5.5x11cm 13.85cm
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Good. I suspected you might have reported lens size.
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Part B
We have a 8.5cm diameter glass jar containing water. The lights are shut off in the room and the only light coming in is the light coming from the door to the hallway being cracked open. The jar is set 5 meters from the door. We then position a domino behind the jar.
We then move the domino away from the jar until the image of the light from the door becomes clear and record the distance the domino is from the back side of the jar.
The measured distance between the jar and domino was 3.1cm.
Part C
The previous experiment is performed but the jar is placed 8.7 meters from the door. The measured distance from jar to the domino was 4.3cm.
Part D
In this experiment a candle is burning in a dark room. A glass jar of diameter 8.5cm containing water placed at varying distances from the flame. A domino is placed on the opposite side of the jar from the candle and moved until the image of the flame is clear.
The distance from the center of the jar to the face of the domino is recorded.
The first column is distance from flame to center of jar, second column is distance from center of jar to face of domino.
40cm 10.5cm
30cm 11.9cm
20cm 14.1cm
10cm 46.2cm
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Your data seem to be consistent with the data obtained by other observers, in that the closer the candle was to the lens the further the image formed from the lens.
You are also consistent in your observation that the distance of the image from the jar increased with increasing distance from the door.
However in one case increasing distance of the object from the lens resulted in increasing distance to the image, while in the other this resulted in decreasing distance of the image from the lens.
Is it possible that experimental uncertainty could explain this discrepancy?
Is it possible that this is really the way refraction would work to form the images?
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It is possible that experimental uncertainty could explain that when the jar was further from the door the distance to the image also increased. Light shining through the door was not really a very clear image to try to focus, If we were focusing a more clear image we definately could get a much more precise measurement.
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Good descriptions.
Your data for the first part of the experiment differed quite a bit from the data reported by others. I've asked you to double-check your data on that part.
Data on the rest of the experiment is consistent with other data I've received.
Please answer the questions I've posed by inserting your answers into a copy of this document, and use **** before and after each insertion.
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Good revision, and good answers.
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