Matter and Radiation

Matter and Radiation

1. 1.1 Inside the atom

   • Nucleus (positively charged)
     • Protons (aka Nucleon)
       • Charge - +1.6x10^-19 C
       • Mass - 1.67x10^-27 Kg
     • Neutrons (aka Nucleon)
       • Charge O C
       • Mass - 1.67x10^-27Kg
     • Held by Electrostatic force
     • Total number of Protons and neutrons is called the nucleon number or mass number
   • The structure of the atom
     • Electrons surround it
       • Charge - -1.6x10^-19 C
       • Mass - 9.11x10^-31Kg
     • Specific Charge
       • Charge/Mass
   • Isotopes
     • Same elements with different no. of neutrons

2. 1.2 Stable and unstable nuclei

   • Strong Nuclear force
     • Isotopes held with the Strong Nuclear force
       • Over-power electrostatic repulsion
       • Hold protons and neutrons together
     • Range of 3-4 femtometres (fm)
     • Effects two neutrons, two protons and neutron and proton
     • At separation greater it is repulsive
   • Radioactive decay
     • Alpha radiaton
       • Consists of two proton and tow neutrons
       • 4
       • a
       • 2
       • Example:____________________
     • Beta Radiation
       • Created when a neutron in the nucleus changes into a proton
         • Fast electron is released emitted
       • 0
       • -1
       • B
       • An antineutrino is emitted
       • Example:_____________________
     • Gamma Radiation
       • Electromagnetic radiation emitted by an unstable nucleus
         • Passes through metal plates
         • No charge or mass
         • Emitted when a nucleus has too much energy

3. 1.3 Photons

   • Electromagnetic waves
     • All electromagnetic waves travel at speed of light
       • 3.0x10^8 ms-1
     • Equation: Wavelength: speed of light/frequency
       • 1nm=10^-9
   • Electromagnetic waves are emitted when a charged particle loses energy
     • When a fast moving electron is stopped
     • an electron moves to a different shell of an atom
   • packet of electromagnetic waves
     • Photon energy:E = hf
       • h=Planck constant= 6.63x10^-34
     • Photoelectricity

4. 1.4 Particles and antiparticles

   • When a particle and anti of the same kind they destroy each other
     • Radiation is released
   • Positron - Electron
     • 2 Gamma Photons are made
     • Positron emission:
       • A neutrino (v) is emitted
   • Annihilation
     • Antiparticle --><--particle
       • Photon
       • Photon
     • Minimum energy of photon: hf = E
   • Pair Production
     • Photon
       • <-- Particle
       • <-- Antiparticle
     • Minimum energy of photon needed: hf = 2E
   • Particles, Anti and E=mc^2
     • 1 MeV = 1.6x10-13 J

5. 1.5 How particles interact

   • The electromagnetic force
     • The momentum of an object is its mass x velocity
     • When two objects interact they exert = forces on each other
     • EF between two objects is due to an exchange of virtual photons
       • p p
       • p p
       • vvvvvvvvv
       • y = Virtual photon
   • The weak nuclear force
     • Weaker than Strong force
     • exchange particles called W bosons
       • Zero mass
         • very short range (0.001 fm)
           • both positively and negatively charged
             • W -
               • Neutrino - Neutron = proton + electron
             • W+
               • Anti neutrino - proton = neutron and positron
             • vvvvvvvv
             • n P
             • p anti ne
             • p e
               • vvvvvvvvvvv
               • n ne
   • Back to Beta Decay
     • B+ Decay
       • vvvvvvvvvvv
         • B+
         • n
         • Neutrino
         • p
         • w+
     • B- Decay
       • vvvvvvvvvvvv
         • w-
         • n
         • p
         • B-
         • Antineutrino
   • Electron Capture
     • vvvvvvvvv
       • w+
       • n v
       • p e