Atoms And Nuclei Question 403

Question: A 7Li target is bombarded with a proton beam current of 104 A for 1 hour to produce 7Be of activity 1.8×108 disintegrations per second. Assuming that one 7Be radioactive nucleus is produced by bombarding 1000 protons, determine its half-life.

Options:

A) 8.6×106s

B) 4.2×105s

C) 3.1×105s

D) 1.1×106s

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Answer:

Correct Answer: A

Solution:

  • The total number of protons bombarded

=itλ=104×36001.6×1019=22.5×1017

Number of 7Be produced N=22.5×10171000=22.5×1014

We know that activity A=λN or A=(0.693t1/2)N
,t1/2=0.693NA=0.693×22.5×10141.8×108 =8.63×106s



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