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1)

 The half-life of radioactive Radon is 3.8 days. the time at the end of which 1/20 th of the radon sample will remain undecayed is (given  log10e=0.43434)


A) 3.8 days

B) 16.5 days

C) 33 days

D) 76 days

Answer:

Option B

Explanation:

t1/2  =3.8 day

     λ=0.693t1/2=0.6933.8=0.182

 If the initial number of atom is a = A0 then after time r the number of atoms is a/20= A , we have to find t.

 t=2.303λlogA0A=2.3030.182logaa/20

  =2.3030.182log20=16.46  days