Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Part 7 - Multiple-Choice Practice Exam: 13


A radioactive sample has a half-life of one hour. If we start with 1 g of it at noon, how much remains at 3 PM? It is 0.125 g.

Work Step by Step

After one half-life, at 1pm, we are down to one-half the original amount, or 0.5 g. After two half-lives, at 2pm, we are down to one-quarter the original amount, or 0.25 g. After three half-lives, at 3pm, we are down to one-eighth the original amount, or 0.125 g. This is discussed on page 625.
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