physics y10 mock

• Irradiation and contamination
• Ionising radiation can damage cells. This may kill the cell or cause mutations in cell DNA that may lead to cancer.
• To reduce the dose of radiation

  1. Decrease the time of exposure

  2. Block the radiation with materials such as lead
• Keeping at a distance from a source


  Allows the radiation to spread out with distance and miss you, or be absorbed by the intervening air
• Radioactive contamination


  The unwanted presence of material containing radioactive atoms
• Irradiation


  When an object is hit by nuclear radiation
• An irradiated object does not become radioactive. (This is a common misconception.)
• Students should be able to compare the hazards (dangers) associated with contamination and irradiation.
• It is important for the findings of studies into the effects of radiation on humans to be published and shared with other scientists so that the findings can be checked by peer review.
• The exam will not test background radiation, or the medical use of radioisotopes.
• New experimental evidence may lead to a scientific model being changed or replaced.
• Solid atoms model


  • Atoms were thought to be tiny solid spheres
• Plum pudding model

  • Atom is a solid ball of positive charge with negative electrons stuck inside it
• Alpha-particle scattering experiment


  1. Alpha particles were aimed at a very thin gold sheet placed in a vacuum

  2. Most particles did pass through the foil but some were deflected significantly and a very few returned backwards
• The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was positively charged
• Bohr's nuclear model


  • Electrons orbit the nucleus at specific distances
• Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.
• The experimental work of Chadwick provided evidence to show the existence of neutrons within. This was about 20 years after the nucleus became an accepted idea.