Textbook Problem

143 views

If the half-life of a radioisotope is 20,000 years, then a sample in which three-quarters of that radioisotope has decayed is ______ years old.

1. a. 15,000
2. b. 26,667
3. c. 30,000
4. d. 40,000

Summary Introduction

Introduction: Half-life is the time taken for one-half of atoms of radioactive isotope to decay which is a characteristic of a radioisotope. The radiometric dating is a technique by which the fossils or age of a rock can be determined using the half-life calculations.

Explanation of Solution

Reason for correct answer:

Half-life is the time taken for one-half of atoms of radioactive isotope to decay. Given that the half-life of a radioisotope is 20,000 years. This means that the real life of that radioisotope will be 40,000, which will be one-half of atoms that has decayed.

Option d. is given as “40,000”.

Half-life is the time taken for one-half of atoms of radioactive isotope to decay.

Hence, the correct answer is option d.

Reason for incorrect answer:

Option a. is given as “15,000”...