Chap 1

• What is the strong nuclear force responsible for?

  Holding protons and neutrons together
• Why do some nuclei remain stable?

  They have a balance of forces within
• What happens during radioactive decay?

  An unstable nucleus releases radiation
• What is emitted during alpha particle emission?

  Alpha particles consisting of two protons and two neutrons
• How does the strong nuclear force behave at distances greater than 1–4 femtometres?

  It becomes repulsive beyond that range
• What is the effect of the strong nuclear force between protons and neutrons?

  It is attractive between all nucleons
• What happens to the nucleon number during alpha decay?

  It decreases by 4
• What is the range of the strong nuclear force?

  1–4 femtometres
• What happens to the atomic number during alpha decay?

  It decreases by 2
• What is a photon?

  A packet of electromagnetic waves
• How is energy emitted as photons?

  When a charged particle loses energy
• What is the speed of light in a vacuum?

  $3.00 \times 10^8 \text{ ms}^{-1}$
• What is the relationship between wavelength and frequency of electromagnetic waves?

  c = fλ
• In what units is wavelength often expressed?

  Nanometres (nm)
• What is the photoelectric effect?

  Emission of electrons from a metal surface
• What are the main types of radiation released by naturally occurring radioactive isotopes?

  • Alpha radiation
  • Beta radiation
  • Gamma radiation
• What are the key points about the strong nuclear force?

  • Holds nucleons together
  • Range: 1–4 femtometres
  • Attractive between nucleons
  • Repulsive beyond 1–4 femtometres
• How do electromagnetic waves behave when emitted by charged particles?

  • Emitted when energy is lost
  • Can occur during electron movement
  • Travel at the speed of light
• How does the photon theory relate to the photoelectric effect?

  • Photons cause electron emission
  • Established by Einstein in 1905
  • Explains light interaction with metals
• What is antimatter?

  Antimatter is the opposite of matter.
• What happens when a particle meets its antiparticle?

  They destroy each other and release energy.
• What is the purpose of PET scans?

  To visualize internal body structures.
• What does PET stand for?

  Positron Emission Tomography.
• What type of tracer is used in PET scans?

  A positron emitting isotope.
• What occurs during the annihilation of a positron and an electron?

  Gamma photons are produced and emitted.
• What is the charge of a positron?

  Positive charge.
• What is emitted alongside a positron during positron emission?

  A neutrino.
• Why are positron-creating isotopes unstable?

  Due to intense pressures inside the nucleus.
• What happens to the energy during the annihilation of a particle and its antiparticle?

  It produces gamma rays and photons.
• How does the mass of an antiparticle compare to its corresponding particle?

  Nearly the same mass.
• What is the relationship between kinetic energy and photon energy during annihilation?

  Kinetic energy converts into photon energy.
• What type of imaging is PET used for?

  Brain imaging.
• What is the minimum energy of a photon required for pair production?

  1.875 MeV.
• Why can't a 2 MeV photon produce a proton-antiproton pair?

  It lacks sufficient energy for that pair.
• What is the rest energy of an electron?

  0.511 MeV.
• What happens during positron emission from a proton-rich nucleus?

  A proton changes into a neutron.
• How does pair production differ from positron emission?

  Pair production creates both particles simultaneously.
• What is the electromagnetic force?

  A force that attracts or repels charged particles.
• What is an exchange particle?

  A particle that mediates interactions between particles.
• What is the weak nuclear force?

  A fundamental force responsible for beta decay.