Understanding Half-Life and Radioactive Decay

What is the definition of half-life in the context of radioactive decay?

• The time required for a quantity to reduce to half its initial value.

• The time taken for a substance to completely decay.

• The time taken for a substance to double in mass.

• The time required for a quantity to reduce to one-fourth its initial value.

Which of the following is NOT a method to measure radioactivity?

• Calculating the number of emissions per minute.

• Measuring the temperature of the substance.

• Counting the number of atoms.

• Measuring the mass of the substance.

If a radioactive sample's mass is 20g initially, what will it be after one half-life?

• 5g

• 0g

• 10g

• 15g

What happens to the activity of a radioactive sample after one half-life?

• It reduces to half.

• It remains the same.

• It becomes zero.

• It doubles.

After two half-lives, what fraction of the original quantity remains?

• 1/16

• 1/4

• 1/8

• 1/2

What does the curve of a radioactive decay graph represent?

• An exponential increase in quantity over time.

• A linear decrease in quantity over time.

• An exponential decrease in quantity over time.

• A constant quantity over time.

What is the symbol used to denote half-life?

• t 1/2

• t 4/1

• t 1/4

• t 2/1

In the example problem, how many half-lives are needed for the number of atoms to fall to 4.5 * 10^17?

• 4 half-lives

• 1 half-life

• 3 half-lives

• 2 half-lives

What is the total time taken for the number of atoms to fall to 4.5 * 10^17 if the half-life is 8 hours?

• 32 hours

• 16 hours

• 8 hours

• 24 hours

Why is it suggested to use common sense instead of equations for certain half-life problems?

• Common sense is more accurate than equations.

• Equations are not available for half-life problems.

• Common sense is faster and simpler for multiples of the half-life.

• Equations are always incorrect.