GREPhysics.NET: GR9277 #49

GR9277 #49

Problem

GREPhysics.NET Official Solution

\prob{49}
Two horizontal scintillation counters are located near the Earth's surface. One is 3.0 meters directly above the other. Of the following, which is the largest scintillator resolving time that can be used to distinguish downward-going relativistic muons from upwards-going relativistic muons using the relative time of the scintillator signals?

1 picosecond
1 nanosecond
1 microsecond
1 millisecond
1 second

Advanced Topics $\Rightarrow$ }Scintillator

The maximal speed the muons can travel at is slightly less than c. Thus, since the distance is $x=3m$ , the time required would be $c=x/t \Rightarrow t=x/c=1E-8$ . The largest scintillator time is the one closest to this, which is 1 ns, as in choice (B).

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Comments

evanb 2008-06-23 18:57:17	A useful fact is that c is just about 1 foot per nanosecond. 3 meters is about 10 feet, so the flight takes about 10 nanoseconds, so we have to be able to resolve on the order of 1 nanosecond to say for sure. Reply to this comment
SonOfOle 2006-11-02 23:29:58	The answer isn't (B) only because it's closest to 10^-8, but also because there must be more than one sample in the time it takes for the muon to pass through. Thus, the answer must also be less then 10^-8. Reply to this comment

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The answer isn't (B) only because it's closest to 10^-8, but also because there must be more than one sample in the time it takes for the muon to pass through. Thus, the answer must also be less then 10^-8.

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