Question: 10 Radioactive isotopes used in biology undergo exponential radioactive decay over different time…

10 Radioactive isotopes used in biology undergo exponential
radioactive decay over different time-spans for different isotopes.
In radioactive decay, the number of neutrons and/or protons of the
isotope decrease and the isotope emits “radioactive” energy that
can be measured with a Geiger counter, typically as counts per
minute (cpm). 32P is a radioactive isotope that has a half-life of
14.3 days (and a decay rate constant, k, of 0.0485), which means
that 50% of the original radioactivity of this isotope has been
emitted in this 14.3 days. In an experiment with some dividing
bacteria in culture, biologists exposed these bacteria to 32P for a
half hour, and let’s say that the bacteria being used divide every
20 minutes. Thus, lots of bacteria incorporate 32P into their DNA.
Immediately after exposure to 32P, they extract the DNA from these
bacteria, and measure the radioactivity of 32P in the DNA. They
report that it is 1.00 × 108 cpm per µg of DNA. They save this
extracted DNA so it can be measured at a later time. What will the
cpm per µg of this DNA be 9.3 days later, expressed in scientific
notation?