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[Phys-l] Alpha decay intensity against distance



Hi,

my colleague showed me an exam question on alpha decay intensity against distance in the air. The data was supposedly taken with and without
placing a paper between the source and the detector. Both graphs looked
like exponential decrease. Well, alpha particles do not generally reach distances approaching 0.5 m in the air and not many (if any?) alpha
particles can penetrate through a piece of paper. So I concluded that
the data was fake.

However, I got curious on what would a real data look like? What might the relationship between distance and intensity be in the case of alpha particles? One may assume that all alphas have the same energy (say 5 MeV).
Their range is within a few centimeters (< 5 cm) in the air as indicated
by the Bragg curve:
<http://en.wikipedia.org/wiki/File:Bragg_Curve_for_Alphas_in_Air.png>

BTW, what radioactive source could be used for this experiment as
there usually are daughter nuclei present emitting gamma and/or
beta radiation?

Best regards,

Antti



Antti Savinainen, Ph.D., B.Ed.
Adjunct Professor (University of Jyväskylä)
Senior Lecturer in Physics and Mathematics
Kuopion Lyseo High School
Finland
E-mail: <antti.savinainen@kuopio.fi>
Website: <http://kotisivu.dnainternet.net/savant/>


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