GR92#25 particle physics

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Joined: Tue Oct 25, 2005 11:29 am

GR92#25 particle physics

Postby kolndom » Tue Nov 08, 2005 1:27 am

25. In experiments located deep underground, the two types of cosmic rays that most commonly reach the experimental apparatus are
(A) alpha particles and neutrons
(B) protons and electrons
(C) iron nuclei and carbon nuclei
(D) muons and neutrinos
(E) positrons and electrons

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Postby danty » Tue Nov 08, 2005 10:22 am

The question is similar to " what kinds of particles can pass through a very
thick layer of matter without interacting with it or being absorbed by it."

It is a well known fact that neutrinos have an extremely small possibility of interacting with matter. As an example of this, the possibility that a cosmic neutrino passes through the earth with out any interaction with matter, is much greater than is in the opposite case!

To be honest, I don't know in what extent does this apply for muons, but since in choice D neutrons are included, D is the correct answer.

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Postby eanzenberg » Tue Nov 08, 2005 11:54 am

Muons can be detected pretty near the surface of earth, maybe 10m down by using cherenkov techniques. Neutrinos are in another ballgame, they need underground detectors. Another badly worded GRE problem that hopefully never sees the light again!

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