Nuclear physics

• What did Rutherford scattering demonstrate?

  The existence of a nucleus
• What model did scientists believe in before Rutherford's experiment?

  Thomson’s plum pudding model

  
• What does Thomson’s plum pudding model suggest about the atom?

  It is a sphere of positive charge

  
• What was the outcome of Rutherford scattering?

  It led to the nuclear model of the atom

  
• What components were included in Rutherford’s apparatus?

  An alpha source and gold foil
• Why was the chamber in Rutherford's experiment evacuated?

  To prevent interference from air particles
• What was used to observe the path of alpha particles?

  A microscope
• What would be expected if the plum pudding model was true?

  Alpha particles would be slightly deflected
• What did the observation that most alpha particles passed through the foil suggest?

  The atom is mostly empty space
• What did the deflection of a small amount of particles by a large angle suggest?

  The center of the atom is positively charged
• What does it imply if very few particles were deflected back by more than 90°?

  The center of the atom is very dense
• What is the conclusion drawn from Rutherford's experiment?

  The atom has a small, dense nucleus

  
• What is radiation in the context of radioactivity?

  Emission of energy from an unstable nucleus
• What are the three types of radiation?

  Alpha, beta, and gamma radiation

  
• How can you identify the type of radiation emitted from a source?

  By measuring count rates with materials
• What happens if the count rate decreases significantly with paper?

  The source emits alpha radiation
• What does a significant decrease in count rate with aluminium foil indicate?

  The source emits beta radiation
• What does a significant decrease in count rate with lead indicate?

  The source emits gamma radiation
• How is radiation used in monitoring material thickness?

  • Beta radiation for aluminium foil
  • Alpha radiation for paper
  • Gamma radiation for steel sheets
  • Detector measures radiation passing through material

  
• Why is gamma radiation used in medicine?

  It causes less damage to the body
• What is one use of gamma radiation in medicine?

  As a detector for diagnosis
• How does gamma radiation sterilize surgical equipment?

  It kills bacteria present on the equipment
• What is a risk of using gamma radiation in radiation therapy?

  It can kill healthy cells
• What is the inverse square law in relation to gamma radiation?

  Intensity decreases with distance squared
• How can you verify the inverse square law experimentally?

  Measure count rate at different distances
• What is the decay constant denoted by?

  The letter λ
• What does the decay constant represent?

  Probability of a nucleus decaying per unit time

  
• What is the formula for calculating the change in the number of nuclei?

  ΔN = -λΔt
• What does the exponential decay formula represent?


  N = N₀e^(-λt)
• What is the half-life of a radioactive sample?

  Time taken for nuclei to halve
• How can half-life be determined graphically?

  By plotting nuclei against time

  
• What is the relationship between activity and the number of nuclei?

  Activity is proportional to the number of nuclei

  
• What is the formula for activity?

  A = λN
• How does the half-life affect the use of radioactive nuclei?

  It determines their application in dating
• What is carbon-14 used for?

  Dating organic objects
• What is Technetium-99m used for in medicine?

  As a radioactive tracer
• What is the half-life of Technetium-99m?

  6 hours
• What are the safety measures for handling radioactive sources?

  • Use long handled tongs
  • Store in lead-lined container
  • Keep distance from others
  • Never point towards others
• What is background radiation?

  Radiation present in the environment
• Why is it important to measure background radiation?

  To find the corrected count rate