Half-Lives

Add the labels to the graph.

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c

d

f

e

a

x-axis

original amount

2nd half-life

first half-life

y-axis

3rd half-life

What percent of Iodine-131 remains after 2 half-lives?

Mathematical Equivalence

OFF

In days, how long is the half-life of Iodine-131?

Mathematical Equivalence

ON

After four half-lives, how many days have passed?

Mathematical Equivalence

ON

The y-axis of the graph measures "counts per second." What does this refer to?

• How many atoms a person can count in a second

• How much radiation is detected by a Geiger-Muller counter per second

• How many atoms there are in a second

• How many atoms there are in the sample

What was the starting "counts per second" of the sample?

Mathematical Equivalence

OFF

After the first half-life, how many counts per second are measured?

Mathematical Equivalence

OFF

How long is the half-life in hours?

Mathematical Equivalence

OFF

After 3 half-lives, how many counts per second would the Geiger-Muller Counter measure?

• 68,000 counts per second

• 35,000 counts per second

• 9,000 counts per second

• 40,000 counts per second

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