Particles and Radiation

• #tags column:12
• Diameter of an atom 10-10 m
• Diameter of the nucleus 10-15 m
• 1e 1.6*10-19 C
• Charge of an electron -1.6*10-19 C
• Charge of a proton 1.6*10-19 C
• Charge of a neutron 0
• Mass of an electron 9.11*10-31 kg
• Mass of a proton 1.67*10-27
• Mass of a neutron 1.67*10-27
• Relative mass of an electron 0.0005 or 1/2000
• Relative mass of a proton 1.0000
• Relative mass of a neutron 1.0004
• Isotope Nucleus with the same proton number but a different nucleon number
• Constituent of an atom with the largest charge-to-mass ratio Electron
• Constituent of an atom with the smallest charge-to-mass ratio neutron
• Nuclide notation ""
• Use of isotopic data Carbon dating
• Unstable isotope may be radioactive, undergoes spontaneous nuclear decay and emits ionising radiation
• Formula for specific charge Q/m
• Strong interaction/nuclear force the force that holds the nucleons together; repulsive below 0.5 fm, attractive up to 3 fm
• Equation for alpha decay ""
• Equation for beta minus decay ""
• Equation for gamma decay ""
• Why was the existence of the neutrino hypothesised? To account for conservation of energy in beta decay
• Photon a packet of energy released in elecromagnetic waves
• Planck's constant 6.63*10-34
• Formula for photon energy (1) E = hf
• Formula for photon energy (2) E = hc/λ
• Formula for the speed of light c = fλ
• For every particle, there is an antiparticle
• Features of an antiparticle same mass as the corresponding particle, the opposite charge
• Annihilation The process that occurs when an antiparticle and particle meet; all their mass is converted into 2 photons
• Antiparticles of the proton, neutron and electron Antiproton, antineutron, positron
• Beta-plus decay- AKA positron emission- Only occurs in experiments- Occurs when there are too many protons in the nucleus
• Positron Emission Tomography (PET scans)- A positron emitting isotope is given to the patient- Some reaches the brain- Positrons only travel a few micrometres before annihilating with electrons- The photons released by annihilation are detected externally
• What is conserved in annihilation? Momentum, energy and antimatter:matter ratio
• Electron volts- A unit of energy- Equivalent to 1.6*10-19 J- Equal to the amount of KE gained by an electron accelerated by a p.d. of 1V- 1 MeV = 1.6*10-13 J
• Formula to convert energy in J to energy in MeV E/(1.6*10-13)
• Fundamental forces Strong Nuclear, Weak Force, Electromagnetic, Gravitational