| The rate at which the unstable nuclei in a radioactive source decay. | Activity |
| What is activity in the context of radioactive decay? | Activity is the rate at which the unstable nuclei in a radioactive source decay. |
| Nuclei that undergo radioactive decay, emitting radiation in the process. | Unstable Nuclei |
| What do radioactive sources contain? | Radioactive sources contain lots of unstable nuclei. |
| The process by which an unstable atomic nucleus loses energy by emitting radiation. | Radioactive Decay |
| What happens to some of the nuclei in a radioactive source at any point in time? | Some of the nuclei in a radioactive source will be decaying at any point in time. |
| What does it mean that radioactive sources are always emitting radiation? | It means that radioactive sources are always undergoing decay and emitting radiation. |
| The becquerel (Bq), which measures the rate of radioactive decay. | Unit of Activity |
| What is the unit of activity? | The unit of activity is the becquerel (Bq). |
| The SI unit of radioactivity, equivalent to one decay per second. | Becquerel (Bq) |
| What does it mean for a source to have an activity of 1 Bq? | It means that one nucleus decays per second in that source. |
| An isotope that undergoes radioactive decay, emitting radiation in the process. | Unstable Isotope |
| Do all unstable isotopes have a specific characteristic? | Yes, all unstable isotopes have a specific half-life. |
| The process by which an unstable atomic nucleus loses energy by emitting radiation. | Radioactive Decay |
| Is radioactive decay predictable? | No, radioactive decay is random, meaning you can't predict when a particular unstable nucleus will decay. |
| The time it takes for half of the undecayed nuclei in a radioactive isotope to decay. | Half-Life |
| What is the half-life of a radioactive isotope? | The half-life is the time it takes for half of the undecayed nuclei in a radioactive isotope to decay. |
| The rate at which a radioactive isotope decays, typically measured in becquerels (Bq). | Activity |
| How is the half-life related to the radioactive activity of a sample? | The half-life of a radioactive isotope is the time it takes for its radioactive activity to fall to half of its original value. |
| The probability that a given nucleus of an isotope will decay per unit of time. | Decay Constant |
| Does the half-life of a radioactive isotope change over time? | No, the half-life of a radioactive isotope remains constant over time. |
| A graph showing the decrease in radioactive activity of a sample over time. This graph shows a radioactive isotope with a half-life of 2 days. After 10 days, the activity of this radioactive isotope has fallen from 80 Bq to only 2.5 Bq. | Radioactive Decay Curve |
| How does the activity of a radioactive sample change over time? | The activity of a radioactive sample decreases over time as the number of undecayed nuclei decreases. |
| A technique used to determine the age of materials based on the decay of radioactive isotopes. | Isotopic Dating |
| How can we use the concept of half-life in isotopic dating? | We can use half-life to estimate the age of materials by measuring the remaining amount of a radioactive isotope and knowing its half-life. |
| The time it takes for half of the undecayed nuclei in a radioactive isotope to decay. | Half-Life |
| What can you determine from a graph of activity against time for a radioactive sample? | You can find the half-life of the sample. |
| The rate at which a radioactive isotope decays, typically measured in becquerels (Bq). | Activity |
| How do you find the initial activity of a radioactive sample from the graph? | Find the activity when the time is zero. |
| What do you do after finding the initial activity on the graph? | Halve the initial activity value. |
| How do you determine the half-life from the graph after halving the activity value? | Draw a horizontal line from the halved value to the curve, then draw a vertical line down from the curve to the x-axis. |
| What does the x-axis value where the vertical line meets represent? | The half-life of the radioactive sample. |
| How can you verify the correctness of your determined half-life value? | Check if it takes another half-life for the activity to halve again. |
| Using a ruler to accurately measure distances or lengths on a graph or physical object. | Ruler Measurement |
| How do you ensure accuracy when drawing lines on the graph to determine the half-life? | Use a ruler to draw precise horizontal and vertical lines from the halved value to the curve and then to the x-axis. |
| The process of determining the change in activity or number of undecayed nuclei of a radioactive sample over time based on its half-life. | Decay Calculation |
| How can the half-life of an isotope be used to predict changes in the activity of a sample over time? | By performing decay calculations. |
| Atoms of the same element that have the same number of protons but different numbers of neutrons. | Isotope |
| What is the half-life of caesium-137? | 30 years. |
| The process of determining the activity of a radioactive sample at a given time based on its initial activity and the number of half-lives passed. | Activity Calculation |
| How do you calculate the number of half-lives passed over a given time period? | Divide the time period by the half-life of the isotope. |
| The activity of a radioactive sample at the beginning of the observation period. | Initial Activity |
| What is the next step after determining the number of half-lives passed? | Halve the activity once for each half-life passed. |
| How do you calculate the activity of a radioactive sample at a specific time in the future? | By halving the initial activity for each half-life passed. |
| How does the activity of a sample of caesium-137 change over 150 years? | It decreases from 240 Bq to 7.5 Bq. |
| How can the decay calculation be adapted to determine the change in the number of undecayed nuclei over time? | By halving the number of undecayed nuclei instead of the activity for each half-life passed. |
| The process of determining the time it takes for a radioactive sample to decay to a certain level of activity or number of undecayed nuclei based on its half-life. | Decay Calculation |
| How can the half-life of an isotope be used to predict the time it takes for a sample to decay? | By performing decay calculations. |
| Atoms of the same element that have the same number of protons but different numbers of neutrons. | Isotope |
| What is the half-life of radon-222? | 3.8 days. |
| The rate at which a radioactive sample decays, measured in becquerels (Bq). | Activity |
| How do you determine how many times the activity of a sample needs to halve to reach a certain level? | By dividing the initial activity by the desired activity. |
| How many half-lives are needed for the activity of the radon-222 sample to decrease from 200 Bq to 25 Bq? | Three half-lives. |
| The time it takes for half of the undecayed nuclei in a radioactive isotope to decay, or for the activity of the sample to decrease to half of its original value. | Half-life |
| What is the next step after determining the number of half-lives needed? | Multiply the half-life by the number of half-lives needed. |
| The time it takes for a radioactive sample to decay to a specified level of activity or number of undecayed nuclei. | Decay Time |
| How long will it take for the activity of the radon-222 sample to decrease from 200 Bq to 25 Bq? | 11.4 days. |
