The Deceleration of Alpha Particles in Plastic Food Wrapping Foil

Equipment

Stage, camera holder, source holder, plastic film (Saran wrap), polonium-210, Minipix-EDU

Procedure

  1. Launch the Pixet Basic software and modify settings to the following:
    1. Min Level: 0
    2. Max Level: 100
    3. Measurement Mode: Tracking
    4. Frames: 100
    5. Exposure: 1 s
    6. Sum: uncheck
    7. Color Map: Hot
  2. Mount the MiniPix EDU camera and polonium on the stage.
  3. Keep the source and camera as close as possible and click on the play button.
  4. Repeat the same experiment with a layer of food wrapping foil inserted between the source and the camera.

Results

  1. Initially, we get a peak at 4300 keV (Fig. 1) and when we insert the foil, the energy decreases to 2300 keV (Fig. 2) because the alpha particles lose some of the energy in the foil.


    Figure 1. The alpha particle blobs observed without anything in the path of the alpha particles



    Figure 2. The alpha particle blobs getting smaller and the energy decreasing after passing through the plastic film

  2. The braking force can be determined using the following equation



    where Ek1 and Ek2 are the kinetic energy and d is the thickness of foil which is 12.7 µm (provided by the manufacturer)
  3. Now using Newton’s Second law of motion, the acceleration will be



    where mɑ is the mass of the alpha particle (6.64 x 10-27 kg)

Conclusion

  1. The braking force appears to be too small in the macro world but is significant enough in the micro-world.

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