Half-Life and Radioactive Decay

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

• The time it takes for all radioactive nuclei in a sample to decay.

• The time it takes for half of the radioactive nuclei in a sample to decay.

• The time it takes for a radioactive nucleus to become stable.

• The time it takes for the decay constant to reach zero.

How does an increase in the decay constant (λ) affect the half-life of a radioactive substance?

• It increases the half-life, making the substance decay slower.

• It decreases the half-life, making the substance decay faster.

• It has no effect on the half-life.

• It only affects the initial number of radioactive nuclei, not the half-life.

A radioactive substance has an initial amount of 100%. If its decay curve shows that 50% remains after 1 year, and 25% remains after 2 years, what is the half-life of this substance?

• 0.5 years

• 1 year

• 2 years

• 4 years

Which type of radioactive decay typically has the shortest half-life among the following?

• Alpha decay of Uranium-238

• Beta decay of Carbon-14

• Gamma decay of Barium-137*

• All have similar half-lives.