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If the fraction of the atoms of a radioactive material left after 120years is 1/64,...

Physics
JAMB 2000
If the fraction of the atoms of a radioactive material left after 120years is 1/64, what is the half-life of the material?
  • A. 24 years
  • B. 20 years
  • C. 10 years
  • D. 2 years
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Correct Answer: Option B
Explanation
1/64 is the usual fraction left of any radio active material after 4 half-lives, since 1/64 = (1/2)6
This implies that 6 half lives have elapsed.
Thus 6 half lives = 120 years
∴ 1 half life = 120/6 = 20 years
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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free