Why can positron go unobstructed through lead?

In summary, during Anderson's positron experiment, it was observed that a positron was able to go through a 6mm lead plate in a charged magnetic field. This was initially thought to be similar to the gold foil experiments, but lead, especially in that thickness, is not known for easily allowing particles through. However, it was later discovered that the pair-production mechanism was at play, where high-energy photons striking a lead nucleus produced an electron-positron pair within the plate. These particles then annihilate each other, turning back into gamma rays.
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Can anyone explain why a positron, in a charged magnetic field, is able to go through a 6mm lead plate, as seen in Anderson's positron experiment?

Initially I thought that it could be quite similar to the gold foil experiments, but one of the features of the gold foil experiments is that it is using a VERY thin sheet of gold.

From what I understand lead, especially lead that thick, has the ability to not easily allow particles through.

Am I taking the wrong approach?

http://en.wikipedia.org/wiki/File:PositronDiscovery.jpg
 
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In trying to understand the results of his experiments, Anderson consulted several other prominent physicists, including Robert Oppenheimer. Anderson's discussions with Oppenheimer proved fruitless; however, other physicists were studying cosmic rays like Anderson at this time. Two of them, P.M.S. Blackett and G.P.S. Occhialini, proposed the pair-production mechanism, where high-energy photons, like the gamma rays found in cosmic radiation, will strike a nucleus and produce an electron-positron pair. These particles will annihilate one another after a brief period, turning back into two gamma rays.

It's not that positrons penetrate lead, but positrons are produced within the plate when high-energy gamma rays strike one of the lead nuclei.

For details on the pair-production mechanism, see this article:
http://en.wikipedia.org/wiki/Pair_production
 

1. How is a positron able to pass through lead without obstruction?

Positrons are able to pass through lead without obstruction because they are much smaller in size and have a lower mass compared to protons and neutrons. This allows them to easily maneuver through the gaps in the atomic structure of lead.

2. Does this mean that positrons are not affected by the strong nuclear force?

Positrons are affected by the strong nuclear force, but they have a much shorter range compared to protons and neutrons. This means that the strong nuclear force does not have a significant impact on the movement of positrons through lead.

3. Why can't other particles, such as electrons, also pass through lead unobstructed?

Electrons have a negative charge and are repelled by the negative charge of the electrons in the lead atom. This makes it difficult for them to pass through the dense atomic structure of lead without being deflected or slowed down.

4. Does the energy of the positron play a role in its ability to pass through lead?

The energy of the positron does play a role in its ability to pass through lead. Positrons with higher energies are more likely to pass through lead without interacting with the lead atoms, while those with lower energies may be slowed down or deflected by the electrons in the lead atoms.

5. Is there any potential danger to humans from the passage of positrons through lead?

No, there is no danger to humans from the passage of positrons through lead. Positrons are commonly used in medical imaging and have been found to have no harmful effects on the human body when passing through lead barriers.

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