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P2 Radiation & Life

P2 Radiation & Life. Lesson 3: Ionisation. Starter. Which 3 things affect radiation intensity ?. Starter. Which 3 things affect radiation intensity ? The distance from the source The type and frequency of radiation The number of photons. Objectives.

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P2 Radiation & Life

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  1. P2 Radiation & Life Lesson 3: Ionisation

  2. Starter • Which 3 things affect radiation intensity?

  3. Starter • Which 3 things affect radiation intensity? • The distance from the source • The type and frequency of radiation • The number of photons

  4. Objectives • MUSTunderstand what is meant by ionising radiation • SHOULD understand how ionisation occurs • COULD understand that exposure to ionising radiation can damage living cells

  5. Atoms • Atoms are made up of a nucleus containing protons and neutrons and electrons which wizz around the outside • Neutrons are neutral • Protons are positively charged • Electrons are negatively charged

  6. Key Words • You need to be able to define the following: • Electron • Atom • Molecule • Ion • Ionisation • Ionising radiation • Mutation

  7. Neutral Atoms and Molecules • Normally atoms and molecules have a neutral charge • They have an equal number of protons and electrons • For example a helium atom has two protons and two neutrons

  8. Ionisation • Ions are charged atoms or molecules • Atoms or molecules can be charged if their numbers of protons and electrons are unequal • Ions can be formed by “knocking out” electrons from atoms or by breaking molecules apart • This process of forming ions is known as Ionisation

  9. Ionisation • Radiation that can cause ionisation is known as ionising radiation • Ionising radiation is found at the high frequency end of the electromagnetic spectrum because they carry the most energy • The three types of electromagnet radiation that are ionising are: UV, X-rays, and Gamma Rays

  10. Textbook Answers 1) Ions are charged and atoms are not; ions are charged and molecules are not. 2) a) Positive; b) negative 3) An atom absorbs an X-ray photon. An electron is knocked out of the atom. A positive ion is formed. 4) The photons of radio waves do not carry enough energy to cause ionisation; gamma photons do. 5) Ionisation in the body is a problem because it changes molecules in cells and so changes processes in cells, e.g. causing cancer, or even the death of the cell. 6) Gamma radiation; it is the most energetic form.

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