Physics quiz question: radioactivity after two half-lives

Physics 205B Quiz 7, spring semester 2014
Cuesta College, San Luis Obispo, CA

A sample currently has a certain proportion of radioactive elements, embedded gaseous daughter elements, and inert material (which is not involved in the decay process). __________ depicts this sample two half-lifes from now.

Correct answer (highlight to unhide): (D)

The sample currently has 12 radioactive element squares. After one half-life, there will be six radioactive element squares remaining, and after yet another half-life, there will only be three radioactive element squares remaining. Note that the amount of daughter element squares and inert material squares does not affect the decay process.

Sections 30882, 30883
Exam code: quiz07bC4n
(A) : 5 students
(B) : 2 students
(C) : 5 students
(D) : 26 studentx

Success level: 68%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

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