Particles and radiation

• Rutherford scattering demonstrated existence of the nucleus. Alpha particles fired at a thin gold sheet in a vacuum chamber covered in a fluorescent coating.
• Why was there a fluorescent coating on the vacuum chamber?

  So you can see where the alpha particles hit the inside of the chamber.
• Plum pudding model is by..

  jj thompson. sphere of positive charge with smaller areas of negative charge evenly distributed (represents the plums)
• In the scattering experiment, some particles went straight through meaning the atom is mostly empty space. Some particles reflected right back (only 1/10000) meaning that the mass is concentrated at the centre and the nucleus is 1/10000th of the atom. Some are deflected, showing that the nucleus is positively charged.
• Radiation is

  Where an unstable nucleus emits energy in the form of an EM wave (transverse)
• Alpha

  • 2-10 cm in air
  • highly ionising
  • deflected by electric and magnetic fields
  • absorbed by paper
  • smoke detectors
• beta

  • around 1m in air
  • weakly ionising
  • defected by magnetic and electric fields
  • absorbed by aluminium (3mm)
  • measuring thickness
• gamma

  • infinite range (inverse square law)
  • very weakly ionising
  • not deflected by magnetic or electric fields
  • lead
  • medical uses (MRI‘s) (sterilise equipment)
• Inverse square law of gamma radiation

  intensity = k/ distance^2
• Gamma spreads through the air in all directions evenly
• Absorption spectra is continuous through a cold gas
• Emission spectra is emitted by a hot gas
• Absorption spectra is when discrete wavelengths are absorbed by the electrons in the gas, causing electrons to be excited. the light emitted is missing the wavelengths of the photons absorbed
• Absorption spectra is continous with black lines
• Emission spectra is the spectrum emitted by a substance, with discrete bright lines due to specific wavelengths/ photons being emitted
• Mesons are made of 2 quarks, quark and antiquark pair
• Baryons are made of 3 quarks
• Neutrons quark arrangement is n: udd
• Protons quark arrangement is p:uud
• pions have no strangeness
• Kaons are mesons with strangeness
• Baryons and mesons are a type of?

  hadron
• Leptons are a type of matter and antimatter
• Hadrons are a type of matter and antimatter
• What are the four fundamental forces?

  electromagnetic, gravity, weak nuclear and strong nuclear
• Electromagnetic affects charged particles and exchanges vitual photons
• weak nuclear affects all particles and exchanges W bosons
• Strong nuclear affects hadrons and exchanges pions
• Strong nuclear force binds the nucleons together in the nucleus
• EM/ electrostatic repulsion repels nucleons
• When strong nuclear force and EM repulsion are balanced, the nucleus is stable.
• Strong force is repulsive <0.5 fm
• Strong force is attractive 0.5 - 3 fm with peak at 1 fm
• Strong force is negligible after 3 fm
• charge, Baryon , lepton must be conserved
• Any interaction with leptons must be a weak interaction as leptons don't feel the strong force
• Strangeness is conserved when only hadrons are involved, as this must be a strong interaction.
• Strange particles are created via strong force and decayed (not conserved) via weak
• Strange particle strangeness = -1 , antstrange strangness = 1
• Specific charge is the ratio of charge to mass