1. Half-life

  1. The half-life of a radioactive substance is the time taken for half of its nuclei to decay.
  2. It is denoted by T1/2.
  3. Formula: T1/2 = ln(2)/λ, where λ is the decay constant.
  4. Different isotopes have different half-lives, ranging from fractions of a second to billions of years.
  5. Example: The half-life of Uranium-238 is approximately 4.5 billion years.
  6. The concept of half-life is critical in understanding the stability of isotopes.

2. Decay Constant

  1. The decay constant (λ) is the probability per unit time that a nucleus will decay.
  2. Relation with activity: Activity (A) = λ · N, where N is the number of undecayed nuclei.
  3. Higher decay constants correspond to shorter half-lives and more rapid decay.
  4. Measured in inverse time units (e.g., s-1).
  5. Decay constant is a fundamental property of a radioactive isotope.

3. Applications of Radioactivity

  1. Medical Applications:
    • Cancer treatment: Using radioactive isotopes like Cobalt-60 for radiotherapy.
    • Imaging: Positron Emission Tomography (PET) scans use isotopes like Fluorine-18.
    • Diagnosis: Tracers like Technetium-99m help in detecting abnormalities.
  2. Industrial Applications:
    • Thickness measurement: Radioactive sources are used to monitor thickness in manufacturing.
    • Welding inspection: Gamma radiography detects flaws in welded joints.
  3. Energy Production:
    • Nuclear power plants use fission reactions of uranium and plutonium.
  4. Scientific Research:
    • Radiocarbon dating (C-14 dating) estimates the age of organic materials.
    • Isotopes like Deuterium and Tritium are used in fusion research.
  5. Agricultural Applications:
    • Radioisotopes are used to study plant metabolism and control pests.

4. Key Characteristics

  1. Radioactive decay is a first-order reaction, meaning its rate depends on the number of undecayed nuclei.
  2. The activity of a radioactive material decreases exponentially over time.
  3. The decay constant and half-life are inversely proportional.
  4. All radioactive isotopes eventually decay into stable isotopes.

Category

Questions

  1. What is the half-life of a radioactive substance?
  2. Which factor does the half-life of a radioactive substance depend on?
  3. What is the SI unit of decay constant?
  4. If the decay constant of a substance increases, what happens to its half-life?
  5. What does the term "activity" of a radioactive substance represent?
  6. Which unit is commonly used to measure radioactive activity?
  7. What is the relationship between half-life (T) and decay constant (λ)?
  8. How is the activity of a radioactive sample affected over time?
  9. If the half-life of a sample is 5 years, how much of the substance remains after 10 years?
  10. What is the half-life of carbon-14 commonly used for radiocarbon dating?
  11. What property makes radioactive isotopes suitable for medical imaging?
  12. Which radioactive isotope is used in the treatment of thyroid disorders?
  13. What happens to the half-life of a substance if the temperature is increased?
  14. Which formula gives the remaining quantity of a radioactive substance after time t?
  15. If a radioactive isotope has a decay constant of 0.1s−1, what is its half-life?
  16. What fraction of a radioactive substance remains after 3 half-lives?
  17. Which property of radioactive isotopes is utilized in carbon dating?
  18. What is the main application of Cobalt-60 in industry?
  19. Which law describes the decay of radioactive substances?
  20. If a sample starts with 100 atoms, how many remain after 2 half-lives?
  21. What is the decay constant of a substance with a half-life of 2 hours?
  22. Which radioactive isotope is used in smoke detectors?
  23. What is the half-life of Uranium-238?
  24. Which radioactive isotope is commonly used in cancer radiotherapy?
  25. After 4 half-lives, what percentage of the original radioactive sample remains?
  26. How is the decay constant related to the probability of decay per unit time?
  27. What is the application of radioactive tracers in medicine?
  28. What is the significance of the half-life in radiometric dating?
  29. Which factor does not affect the rate of radioactive decay?
  30. What is the primary application of Technetium-99m in medicine?
  31. Which quantity decreases exponentially in radioactive decay?
  32. If a radioactive isotope has a half-life of 1 hour, how much remains after 3 hours?
  33. What is the unit of activity in the SI system?
  34. How is the age of fossils determined using radioactive isotopes?
  35. Which process is used to date ancient organic materials?