physics topic 4

• What is the focus of Nuclear Physics?

  It studies atomic nuclei.
• Who discovered that atoms are made of charges?

  JJ Thompson
• What model did JJ Thompson propose?

  Plum pudding model
• What did Ernest Rutherford discover about the atom?

  The positive part is very small.
• What is the nucleus of an atom?

  The center containing protons and neutrons.
• What did Niels Bohr discover about electrons?

  They exist in shells or orbitals.
• What are the two types of charges in an atom?

  Protons and neutrons
• What is the atomic number?

  Number of protons in the nucleus.
• What does the mass number indicate?

  Protons plus neutrons in the nucleus.
• How many protons does a carbon atom have?

  Six protons
• What are isotopes?

  Atoms of the same element with different neutrons.
• What does the term radiation refer to?

  Particles or waves emitted by something.
• What is gamma radiation emitted by?

  The nucleus of an atom.
• Why can gamma rays be dangerous?

  They can ionize atoms and damage cells.
• What type of decay do heavier nuclei like americium-241 undergo?

  Alpha decay
• What is emitted during alpha decay?

  An alpha particle (2 protons, 2 neutrons).
• What happens to the atomic number during alpha decay?

  It decreases by 2.
• What is the mass number after alpha decay of americium-241?

  It becomes 237.
• What is beta decay?

  A neutron turns into a proton and an electron.
• What is the charge of a beta particle?

  Negative one
• How does beta decay affect the atomic number?

  It increases by 1.
• What is the ionizing ability of alpha particles?

  High ionizing ability
• What can stop alpha radiation?

  A few centimeters of air or paper.
• What is background radiation?

  Radiation from natural and man-made sources.
• How do you correct radiation counts?

  Subtract background count from source count.
• What is beta radiation used for?

  Detecting thickness of materials.
• What is the penetrating power of gamma radiation?

  High penetrating power
• What materials can reduce gamma radiation intensity?

  Lead and concrete
• What is radioactivity?

  The rate of decay of radioactive sources.
• How is radioactivity measured?

  Using a GM tube.
• What is half-life?

  The time for activity to decrease by half.
• How does the half-life of a radioactive isotope vary?

  It can range from days to millions of years.
• How do you find the half-life from a graph?

  Half the initial number and measure time.
• What happens to the number of unstable nuclei over time?

  It decreases as they decay.
• If a sample starts at 96 Bq and falls to 12 Bq, how many half-lives occurred?

  Three half-lives
• What is the half-life if 12 months equals three half-lives?

  Four months
• What is nuclear fission?

  Splitting a nucleus into smaller nuclei.
• What happens to mass during nuclear fission?

  It decreases, converting to energy.
• What is a chain reaction in nuclear fission?

  Releasing neutrons that cause further fission.
• What is the purpose of a nuclear reactor?

  To control chain reactions for energy production.