Physics Unit 1

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  • Physics Unit 1
    • Atomic  structure
      • Atom has a positively charged nucleus surrounded by negatively charged electrons
      • Protons and neutrons are called nucleons
      • Isotopes are atoms with the same number of protons and diffident number of neutrons
      • A =  Mass or nucleon number
      • Z =  Atomic or proton number
      • Uncharged atoms have equals numbers of protons no electrons
      • A nuclide is a type of nucleus with a particular number of protons and neutrons
      • Specific charge = charge ÷ (nucleon x electron mass)
      • The election has the highest specific charge out of all the other particles
      • The higher the neutron : proton ratio the more unstable the nucleus is
      • The strong nuclear force is an attractive force between nucleons that holds them in the nucleus
        • A range of no more than 3-4 fm
        • Same effect between al nucleons
        • Below a separation of 0.5 fm it is a repulsive force
          • To prevent nucleons from being pushed into each other
      • Alpha radiation consists of alpha particles (2 protons, 2 neutrons)
        • Beta radiation consists of fast moving electrons
          • Gamma radiation is electromagnetic radiation emitted by an unstable nucleus
            • Carries away excess energy
          • Beta minus decay produces an antineutrino
          • Beta plus decay produces a neutrino
      • Wavelength of electromagnetic radiation ? = c ÷ f
        • Electric wave and magnetic wave travel together and vibrate perpendicularly and in phase
          • A charged particle emits EM waves when it loses energy
            • Eg.  When a fast moving electron slows down or changes direction or when an electron moves to a lower energy level in an atom
            • Emitted burst of EM waves are called photons
              • A photon has an energy if E = hf
                • The power of a beam of photon = nhf  where n is the number of photons passing a point per second
      • antiparticles annihilate their     corresponding particles when they meet
        • They have the same rest mass as the particle and opposite charge
        • Annihilation produces two photons (mass is converted to energy)
          • Min energy of each photon = hf = E?
            • For pair production a photon needs an energy hf = 2E?


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