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Questions and Answers
Which radioactive isotope has the highest concentration in sea water?
What is the predominant source of natural radioactivity in the human body?
How much natural radioactivity is typically found in the human body?
Which of the following isotopes is NOT mentioned as a natural radioisotope found in the environment?
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Which two natural radioactive elements are mentioned as accumulating in the human body?
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What form of radiation exposure is primarily provided by the Earth's soil?
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Which isotopes are significant sources of natural radioactivity in drinking water?
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Which natural radioactive element is primarily associated with the activity level of 0.1 Bq/L in ground water?
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What does the variable A(t) represent in the decay rate formula?
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How is the decay rate expressed mathematically at time t = 0?
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Which radioactive isotopes are primarily found in soil and rocks?
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Which building materials contain natural radioisotopes?
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What unit is equivalent to one decay per second?
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What contributes to natural background radiation?
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If 1 Ci is equal to $3.73 × 10^{10}$ decays/s, what is the equivalent number of decays in 1 mCi?
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What is the origin of the terrestrial component of radiation?
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If the decay constant λ is increased, what can be inferred about the decay process?
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What is the formula to calculate the number of decays in terms of half-lives?
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Which series of radioactive elements ends with a stable isotope of lead?
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What does the decay constant (λ) indicate?
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Which of the following best describes the relationship between time (t) and number of undecayed nuclei (N)?
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Which primordial radionuclide has a terrestrial origin?
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If N0 represents 100 nuclei and λ is 0.1, what would be the number of undecayed nuclei (N) after 10 seconds?
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What characteristic do isotopes in the thorium series share?
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Which of the following statements is incorrect regarding half-lives?
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Which of the following is NOT a significant contributor to natural background radiation?
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What does N0 equal in the context of the radioactive decay law?
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What form does the equation N = N0 e^{-λ t} take?
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What does the variable N represent in the radioactive decay law equation?
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In the example of 131I, if the initial activity is 5.0 mCi and it decays to 2.1 mCi, which decay period does it represent?
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What will be the outcome if no radioactive decay occurs?
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How many radon atoms decay in a ~92 m2 house with 4 pCi/L of radon every minute?
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What primarily influences the differences in radon levels in various environments?
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Why does radon have greater mobility compared to uranium and radium?
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Through which type of soil does radon move more readily?
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In what type of environments does radon move more quickly?
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How far does radon typically move before decaying in water-saturated rocks or soils?
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What affects the distance radon can travel in soil before decaying?
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What is the maximum distance radon can travel through dry rocks or soils before decaying?
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Study Notes
Radioactive Decay Law
- Radioactive decay is a first-order process, meaning the rate of decay is proportional to the number of radioactive nuclei present at any given time.
- The decay constant (𝜆) represents the probability per second of a radioactive nucleus decaying.
- The number of undecayed nuclei (N) at time (t) is calculated using the formula: N= N0e−λt , where N0 is the initial number of undecayed nuclei.
Activity of a Sample (Decay Rate)
- The activity of a sample is the number of decays per second.
- It is calculated using the formula: A(𝑡) = A0e−λ𝑡, where A0 is the initial activity, λ is the decay constant, and t is time.
- The activity can also be expressed as: A(𝑡) = A0/2^𝑛, where 𝑛 is the number of half-lives that have occurred.
Unit of Activity
- The Becquerel (Bq) is the standard unit of activity, representing one decay per second.
- The Curie (Ci) is a larger unit, equal to 3.73 × 10^10 decays per second.
- 1 Ci = 3.73 × 10^10 Bq
Natural Radioactivity (Environmental Radioactivity)
- Terrestrial radiation is a significant source of natural radioactivity.
- Important natural radioactive isotopes in the environment include: tritium (3H), carbon (14C), potassium (40K), polonium (210Po), radon (222Rn), radium (226Ra), and uranium (238U).
- These isotopes accumulate in the human body through food, water, and air, contributing to natural radioactivity within humans.
- Seawater contains a substantial amount of potassium (40K), leading to an activity of about 12 Bq/L.
- The natural radioactivity of the human body is approximately 9000 Bq, primarily from potassium (40K) and carbon (14C).
- The soil and rocks of Earth contain naturally radioactive elements such as potassium (40K), radium (226Ra), and thorium (232Th), contributing to natural radiation exposure.
- These elements are also found in building materials like concrete and bricks.
- The terrestrial component of natural radioactivity originates from primordial radionuclides in the Earth's crust.
- Three important radioactive decay series contribute significantly to natural background radiation: uranium, thorium, and actinium.
Radon (222Rn)
- Radon is a naturally occurring radioactive gas produced from the decay of radium (226Ra).
- It is a significant source of natural radiation exposure.
- Radon levels vary depending on the geology of the area, the presence of uranium, and the movement of radon, soil gas, and groundwater.
- Radon is more mobile than uranium and radium, which are fixed in rocks and soils.
- Radon moves more easily through permeable soils (e.g., sand and gravel) than through impermeable soils (e.g., clays).
- Fractures in soil or rocks allow radon to move more quickly.
- Radon in water moves slower than in air.
- Radon travels shorter distances in wet soils than in dry soils before decaying.
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Description
Explore the principles of radioactive decay, including the first-order process, decay constant, and activity calculation. This quiz covers essential formulas and units like Becquerel and Curie. Test your understanding of how these concepts relate to natural radioactivity.
