CW: March 5th: Radiometric Questions

You find a rock sample with radioactive atoms present.  If 12.5% of the original radioactive atoms were present, how many half-lives has the rock been around for? (Hint, at Half-Life = 0, you start with 100%)

• zero
• 1
• 2
• 3

You find a rock sample with radioactive atoms present.  If 25% of the original radioactive atoms were present, how many half-lives has the rock been around for? (Hint, at Half-Life = 0, you start with 100%)

• zero
• 1
• 2
• 3

If the half-life of a radioactive group of atoms is 100 years, then how old is the rock if there have been two half-lives?

• 25 years
• 200 years
• 400 years
• 800 years

Suppose you found a material in which 12.5% of the original radioactive atoms were still present.  If the half-life of an atom is 60 years, how old is the material?

• 30 years old
• 60 years old
• 120 years old
• 180 years old

Using ESRT (A) [Radioactive Decay Data], what is the half-life in standard notation of carbon-14?

• 5,700 years
• 57,000 years
• 570,000 years
• 5,700,000 years

The graph shows the radioactive decay of a 50-gram sample of a radioactive isotope. 
According to the graph, what is the half-life of this isotope? 

• 100 years
• 150 years
• 200 years
• 300 years

The length of time required for half of the radioactive atoms in a sample to decay is its...

• era
• age
• half-life
• eon

Which radioactive element is used to determine the absolute age of late Pleistocene animal remains?

• rubidium-87

• uranium-238

• potassium-40

• carbon-14