Matter and Radiation

Matter and Radiation

1. Inside the atom

   • Every atom contains a positively charged nucleus composed of protons and neutrons and is surrounded by electrons.
     • Protons and neutrons can be referred to as nucleons.
   • Electrons have negative charge and the nucleus has a positive charge which means the electrons are held to the atom by electrostatic forces of attraction.
   • The majority of an atoms mass is in the nucleus.
     • This was discovered through Rutherford's investigations.
   • Isotopes
     • An isotope is an atom with the same number of protons and electrons but a different number of neutrons.
   • Specific Charge
     • Specific charge is charge divided by mass.

2. Stable and Unstable nuclei

   • Strong Nuclear Force
     • The strong nuclear force overcomes the electrostatic force of repulsion between the protons in  the nucleus and holds protons and neutrons together.
     • Range of no more than 3-4 fm
     • Same effect between 2 protons as between 2 neutrons or a proton and a neutron
     • Attractive force from 3-4 fm down to 0.5 fm then becomeds repulsive any lower.
   • Alpha Radiation
     • Consists of Alpha particles which each have 2 protons and 2 neutrons. Nucleon number decreases by 4 and atomic number decreases by 2.
   • Beta Radiation
     • Consists of fast moving electrons. Occurs when a nucleus changes to a proton. Changes the element.
   • Gamma Radiation
     • Electromagnetic radiation emitted by an unstable nuclei.

3. Photons

   • Photon energy E = hf
   • Power of a beam == nhf
   • Photons of light are a small part on a spectrum of electromagnetic waves and is the only section our eyes can detect.

4. Particles and Antiparticles

   • When matter and antimatter particles meet, they destroy each other and release radiation.
   • Dirac's theory of antiparticles
     • Every particle has a corresponding antiparticle that: -Annihilates the particle itself converting total mass into protons -Has exactly the same rest mas -Haas exactly the same opposite charge to the particle if there is one
   • E = mc^2

5. Particle Interactions

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