How far can Alpha Particles Travel?


Stage, camera holder, source holder, polonium-210, Minipix-EDU


  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 the holder with polonium on the stage.
  3. Keep the camera and the source as close as possible and click on the play button.
  4. Next, shift the source to 2 cm and collect the data. Similarly, collect the data for 3 cm and 4 cm.


  1. Initially, when the source is closest, we observe that the frame is full of alpha particles (Fig. 1).

    Figure 1. The blobs of the alpha particle from Po-210 with the camera and source kept as close as possible.

  2. As we reach ~2 cm, the number of observed particles has dropped. Also, the particles are relatively smaller (Fig. 2) which indicates further energy loss because of increased distance of the source from the camera.

    Figure 2. The alpha particle blobs getting smaller at a 1 cm distance between the source and the camera

  3. At 3 cm, we observe a further decrease in the size and density of observed alpha particles (Fig. 3).

    Figure 3. The alpha particle blobs further getting smaller with increasing distance

  4. Approximately at 4 cm, the alpha particles are much smaller (Fig. 4) and if we further increase the distance to 4.5 cm, they disappear.

    Figure 4. The alpha particles losing most of their energy and almost diminishing at a distance of 4 cm


  1. As explained earlier, alpha particles are the heaviest among the three and are more ionizing. They quickly lose their energy in the air and thus have a very short mean linear range.
  2. The alpha particles from polonium-210 have only ~4.5 cm of range.

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