question_answer

Starting with a sample of pure\[^{66}Cu,\] 7/8 of it decays into Zn in 15 min. The corresponding half-life is                                [AIEEE 2005]

A) 10 min

B) 15 min

C) 5 min

D) \[7\frac{1}{2}\] min

Correct Answer: C

Solution :

[c] The number of particles left undisintegrated,

where,decay constant

initial number of atoms

andpresent number of atoms

Taking log both sides, we get

Half life period