The Argon-40 Method of Radioisotope Dating Was Developed in the Geology

question 164

Multiple Choice

The argon-40 method of radioisotope dating was developed in the Geology Department at Stony Brook University to determine the age of rocks brought back from the moon. This method assumes that no argon-40 gas was trapped when the molten rock solidified, and that no argon-40 can escape from the solid rock. One sample that was analyzed had a ratio of potassium-40 to argon-40 of 0.100 (N_K/N_Ar = 0.100) . Potassium-40 decays into argon-40 by positron emission with a half-life of 1.28  10⁹ years. How many years ago was this moon rock formed?

• A)2.6  10 ⁸ years
• B)2.3  10 ⁹ years
• C)4.4  10 ⁹ years
• D)1.3  10 ¹⁰ years
• E)1.3  10 ⁸ years

---

Definitions:

Sample

A subset of individuals or observations selected from a larger population, used to infer or make generalizations about the whole group.

Married

A legal and social status denoting a recognized union, typically between two people, that is often formalized through a wedding ceremony.

Frequency Distribution

A representation, either in graphical or tabular form, showing how often each different value in a set of data occurs.

Area Code

A segment of a telephone number that designates a particular geographical area or jurisdiction for routing calls.