Half-Life and Simple Decay Patterns Quiz

Concept: definition of half-life. Half-life is a statistical time. It describes how long it takes for half the nuclei to decay, not when a specific nucleus will decay.

Concept: meaning of one half-life. That’s the definition. In large samples, the number remaining is about half, even though individual decays are random.

Concept: applying 'half remains.' Half remain. Half-life means the sample is reduced by a factor of 2 after one half-life.

Concept: repeated halving. 1/2 × 1/2 = 1/4. Each half-life halves the amount again, so after two half-lives only one quarter remains.

Concept: half-life applies to amount/mass. Half remains. If the isotope is decaying, the amount of that radioisotope halves after one half-life.

Concept: half-life as an isotope property. It’s a property of the isotope. Changing the sample size changes how many atoms you start with, but not the decay probability per unit time.

Concept: using (1/2)^n. (1/2)^3 = 1/8. Three half-lives means the sample has been halved three times.

Concept: activity definition. Activity measures decay rate. A higher activity means more nuclei are decaying each second.

Concept: fewer nuclei – lower activity. Fewer undecayed nuclei remain. With fewer nuclei available to decay, the decay rate drops.

Concept: units of activity. 1 bq = 1 decay per second. This unit directly counts how many nuclear decays happen each second.

Concept: meaning of the becquerel. That’s the definition. The becquerel measures how active a radioactive source is by counting decays per second.

Concept: step-by-step halving. 64 → 32 → 16 → 8. Each half-life divides the amount by 2, repeated three times.

Concept: randomness vs statistics. Individual decay is random; only large samples are predictable. We can predict probabilities and averages, but not the exact decay time for one nucleus.

Concept: interpreting half-life length. Longer half-life = slower decay. The probability of decay per unit time is smaller, so the sample changes more slowly.

Concept: correct half-life statements. A, B, D are correct; after 2 half-lives, 1/4 remains. Half-life repeats halving, so after two half-lives you have one quarter, not one half.

Concept: exponential decay behavior. Exponential decay approaches zero. The amount becomes extremely small over time, but mathematically it decreases by halves and does not hit exactly zero.

Concept: exponential decay. Radioactive decay follows exponential behavior. The rate depends on how many undecayed nuclei remain, so it keeps decreasing over time.

Concept: two half-lives for 1/4. 1/4 requires 2 half-lives – 2×5=10 years. Halving twice gives one quarter remaining.

Concept: half-life independence from amount. Half-life depends on isotope. Different starting masses only change the starting number of nuclei, not the decay probability.

Concept: half-life summary. Half-life is a decay timescale. It is a practical way to compare how fast different isotopes decay.