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B Available materials for Faraday rotation experiment

  1. Jul 20, 2016 #1
    I am a high school student experimenting with the Verdet constant of materials and how it affects the polarization of light in magneto-rotation. I have trouble acquiring the proper materials for this experiment. Here is what I have so far:

    -AC/DC Power Supply
    -Optical laser under 5MW
    -Neodymium Magnets
    -Various samples that light can pass through

    I need polarisers and light analyzers to complete the apparatus. I also think the neodymium magnets will be too weak to create a magnetic field surrounding my sample. I would appreciate any advice on sustainable polarizers, analysers, and magnets that are relatively cheap (under $60).
  2. jcsd
  3. Jul 20, 2016 #2


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    An easy source for polarizer/analyzer is a pair of polarized sunglasses, Polaroid is one widely available brand. In the U.S., drug stores often carry them. It is easiest to remove the lenses from the ones than clip onto eyeglasses, and they are often the cheapest but a little harder to find. Watch out for very cheap ones, they sometimes are not polarized, just tinted. To check them, grab two pair and check that transmission drops dramatically when rotated with respect to each other.

    Also, not necessarily a problem, but be aware that some lasers are polarized.

    As to magnet strength, you have a Gaussmeter so you can measure them. An online search for 'Verdet constant' should reveal the sensitivity of various materials.

    A somtimes-cheap source for some fairly strong magnets is to tear apart an old computer hard disk drive. Maybe your local computer repair store has a junk one you can talk them out of. After you get the cover off the drive itself you will see the disk recording surfaces and an arm that moves the read/write head(s) across the disk surfaces. The arm is mounted on a motor that, when disassembled, has a few VERY strong magnets. (I use them for refrigerator magnets.)

    Good luck, and let us know how things work out!
  4. Jul 21, 2016 #3
    You can buy polarizer sheets for much less than 60$. Just look online.
    Square pieces (1" size) can be around 1$ a piece.
    Polarizing eyeglasses may be more expensive. Unless you have some you don't need anymore. :smile:
  5. Jul 21, 2016 #4


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    It is possible to see the effect using a glass rod. The rotation is very small and so the effect can only just be seen. One problem you have with permanent magnets is how to remove the magnetic field, so as to see the difference, without disturbing the set up. For this reason, the method in last school used a big horse shoe electromagnet (actually part of the transformer kit) about 10 cm long with 3 cm diameter legs and 1200 turns of wire. It has closely spaced pole pieces having light holes. I am trying to recall the exact geometry.
  6. Jul 21, 2016 #5


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    This link shows the geometry I am describing:-
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