Question

A point source emitting alpha particles is placed at a distance of 1 m from a counter which records any alpha particle falling on its 1 cm² window. If the source contains 6.0 x 10¹⁶ active nuclei and the counter records a rate of 50000 counts/second, find the decay constant. Assume that the source emits alpha particles uniformly in all directions and the alpha particles fall nearly normally on the window.

Answer 1

Counts received per cm² = 50000 Counts/sec.

N = N3o of active nucleic = 6 x10¹⁶

Total counts radiated from the source = Total surface area  50000 counts/cm2

= 4x3.14 x 1 x10⁴x 5 x10⁴ = 6.28x 10⁹ Counts = dN/dt