Nuclear

• What did Rutherford scattering demonstrate?

  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?

  Atom is a sphere of positive charge

  
• What was the new model for the atom called after Rutherford's experiment?

  Nuclear model

  
• What components did Rutherford's apparatus include?

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

  To prevent interference from air particles
• What was the purpose of the fluorescent coating in the chamber?

  To visualize where alpha particles hit
• What was expected if the plum pudding model was true?

  Alpha particles would be slightly deflected
• What did most alpha particles do in Rutherford's experiment?

  Passed straight through the foil
• What did the deflection of a small amount of particles suggest?

  Centre of the atom is positively charged
• What did very few particles being deflected back by more than 90° suggest?

  Centre of the atom is very dense
• What is radiation?

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

  Alpha, beta, and gamma radiation

  
• What is the range of alpha radiation in air?

  2 - 10 cm
• How ionising is alpha radiation?

  Highly ionising
• What absorbs alpha radiation?

  Paper
• What is the range of beta radiation in air?

  Around 1 m
• How ionising is beta radiation?

  Weakly ionising
• What absorbs beta radiation?

  Aluminium foil (around 3 mm)
• What is the range of gamma radiation in air?

  Infinite range
• How ionising is gamma radiation?

  Very weakly ionising
• How can radiation types be identified using a GM tube?

  1. Measure background count.
  2. Measure count rate with source.
  3. Use paper to check for alpha.
  4. Use aluminium foil for beta.
  5. Use lead for gamma.
• What absorbs gamma radiation?

  Several metres of concrete or several inches of lead
• How is beta radiation used in monitoring material thickness?

  • Beta source on one side
  • Detector on the other side
  • Adjust rollers based on count rate
• What are the medical uses of gamma radiation?

  • As a detector for diagnosis
  • To sterilise surgical equipment
  • In radiation therapy for cancer
• What is the inverse square law in relation to gamma radiation?

  Intensity decreases with distance squared
• What is the formula for the intensity of gamma radiation?

  I = k / x^2
• How can the relationship of gamma radiation intensity be investigated?

  Measure count rate at different distances
• What is the danger of alpha radiation if inhaled or ingested?

  Can ionise body tissue
• What can prolonged exposure to gamma radiation cause?

  Mutations and damage to cells
• What safety measures should be taken when 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
• What are some sources of background radiation?

  Radon gas, cosmic rays, rocks
• What is radioactive decay?

  Random process of nucleus emitting energy
• What is the decay constant denoted by?

  λ (lambda)
• How is the decay constant calculated?

  ΔN / Δt over initial number of nuclei
• What does the exponential decay formula represent?

  N = N0 * e^(-λt)
• What is the half-life of a radioactive sample?

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

  Plot nuclei against time and measure halving

  
• What is a more accurate way to measure half-life?

  Plot ln(N0) against time