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. After 
, the count rate has fallen to 
. Both count rates have been corrected for background radiation. What is the half-life of the source?
-particles per second. After 
the rate of emission has fallen to 600 
. The half-life of the radioactive isotope is 
. Which graph shows the decay for this isotope?
. A detector near the source shows a reading of 
. Background radiation can be ignored. What is the reading on the detector 
later?
and a half-life of 
. How long will it take for the rate of emission to fall to 
?
. How long will it take until only one-fourth of this sample remains undecayed?
. It has an initial rate of emission of 
. How long will it take for this rate of emission to fall to 
?
is obtained. The table shows the count rate from the isotope over a three-year period.
on a detector. Which calculation is used to predict the count rate after 12 years?
of a radioactive isotope. After 
the mass of the radioactive isotope in the sample falls to 
. What is the half-life of the radioactive isotope?
. How long will it take for the count rate to drop to 
?
.
.
of the number of emissions per second from a radioactive source. The table shows the readings.
. Predict the count rate from the sample after 60 minutes.
