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Phy 122

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Interference Lab Question

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Lab #29 Interference states:

As best you can, determine for this position the average distance between the distinct bright spots formed on the wall.

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I can't form any distinct bright spots on the wall. I am standing 5 meters from the wall. I have tried holding the laser pointer directly against the transparency and holding it at various small lengths behind the transparency. I still don't get distinct bright spots, just one spot of sometimes differing shape.

I've enlisted my wife to both hold the laser and transparency and to observe the wall while I hold the laser and transparency. No luck.

I've watched the video, but I can't see how you are holding the laser and the transparency.

Any thoughts or tips?

Thanks,

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One of the figures on the transparency is a rectangular grid of parellel lines, half a millimeter or less apart. If the laser beam goes through this grid you should see dots. They won't be perfectly distinct; the dots will be somewhat blurry and a little bigger than the dot formed by just the laset. Some light will also be scattered between them, but you should definitely be able to make out at least three images of the beam.

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Try this and let me know if it doesn't work.

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