How much of the original amount of an isotope is present after a period of two half-lives?A.Four times the original amountB.Half of the original amountC.One-fourth of the original amountD.Twice the original amountSUBMITarrow_backPREVIOUS

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 175 grams of a radioactive isotope, how much will be left after 4 half-lives?

radioactive isotope decays with a rate proportional to the original amountof material present. If originally there is 50mg of the material present and aftertwo hours it has lost 10% of its mass, determine the half-life, the time at which itis half its original mass.

A 490. μg sample of the isotope 234Th is prepared. How much is left after 31.7 days? The half-life of 234Th is 24.1 days. 307 μg 59.0 μg 197 μg 147 μg  Tries 0/2

Strontium-90 is radioactive and has a half life of 28.8 years. What percentage of a sample would be left after 108. years?Round your answer to 2 significant digits.

Which of the following is NOT equal to the half-life of an isotope?Half the time it takes for all of the radioactive nuclei present in a sample to decayThe time it takes for the number of nuclei in a sample of the isotope to halveThe time it takes for the count rate from a sample of the isotope to fall to 50% of its initial valueThe time it takes for the activity of a sample of the isotope to fall to half of its initial level2Which of the following equations links the total count rate from a source, its corrected count rate, and the background count rate?Background count rate = total count rate + corrected count rateTotal count rate = corrected count rate – background count rateCorrected count rate = total count rate – background count rateCorrected count rate = total count rate + background count rate3There are initially 400,000 nuclei present in a sample of radioactive material of half-life 30 minutes.  How many of these nuclei will remain after two hours?100,00050,000200,00025,0004Carbon-11 has a half-life of approximately 20 minutes.  The corrected count rate at a given point in time from a sample of carbon-11 is 160 counts per second.  What would the corrected count rate from the sample have been 40 minutes earlier?320 counts per second80 counts per second40 counts per second640 counts per second5A GM tube is connected to a rate meter.  With no source present, the reading on the rate meter is 12 counts per second.  When a source is brought close to the GM tube, the reading increases to 60 counts per second.  Calculate the corrected count rate from the source.5 counts per second48 counts per second12 counts per second72 counts per second