A cosmic-ray monitor at a mountain station records muon events in a counting interval…

PHYSICS · Multi-part · Fermi University Physics · Scientific Practice & Experimental Methods · Uncertainty in measurement · Uncertainty in measurement

Measurement and Method, Ch Counting experiments: Poisson statistics and the root-n rule

Problem

A cosmic-ray monitor at a mountain station records

n = 180

muon events in a counting interval of

t = 900\,\mathrm{s}

(fifteen minutes); the background is negligible over this interval. Someone calculates the count rate

R = n/t = 0.200\,\mathrm{s^{-1}}

and then writes

u(R) = \sqrt{R} = \sqrt{0.200} = 0.447\,\mathrm{s^{-1}}.

((a)) Say what is wrong with this calculation of

u(R)

. ((b)) Give the correctly calculated rate with its uncertainty.

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