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• Wilhelm Conrad Roentgen (1845 - 1923)

  • In 1895, Wilhelm Conrad Roentgen, a German physicist, discovered X-ray also known as Roentgen rays. He had unintentionally taken an X-ray photograph of his wife’s hand. This success led Wilhelm Conrad Roentgen to receive the first Nobel Prize in Physics in 1901 for the discovery of X-ray.
  • In 2004, as an honour for his achievement, International Union of Pure and Applied Chemistry (IUPAC) named the 111th element (radioactive element) as roentgenium in conjunction with the name Roentgen

  
• X-ray

  • X-ray are a form of electromagnetic radiation slightly similar to visible light but with different features
  • X-rays could penetrate a number of materials including human body tissues and enable us to view bones as well as metals and create s shadowy images of structures like bones, organs, sings of diseases or injuries, and detect break or fracture of bone
• Antoine Henri Becquerel

  • In 1896, Antoine Henri Becquerel, a French physicist, became the first person to successfully discover radioactivity. He found a radioactive compound, uranium and unintentionally produced rays that can blacken a photographic plate even in the dark. The rays were detected based on the ionising property. Due to this, Antoine Henri Becquerel received the Nobel Prize in Physics in 1903 for the discovery of radioactivity.
  • Awarded the Nobel Prize in Physics together with Marie and Pierre Curie in 1903
• Introduction of Marie Curie (1867 - 1934) and Piere Curie (1859 - 1906)

  • Henri Becquerel's findings on radioactivity became an inspiration for this couple to investigate further on many materials to find signs of radioactivity phenomenon
  • At the end of 1897, this married couple from Poland, successfully detected radioactive radiation through its ionising power and not through the photographic effect. Beginning with uranium ore which is known as pitchblende, they successfully extracted two radioactive elements, polonium and radium.
  • Both awarded the Nobel Prize in physics in 1903
• Marie Curie

  • Famous Poland physicist and chemist
  • First woman to be awarded the Nobel Prize and the first person to win Nobel in two fields, Physics (1903) and Chemistry (1911)
  • Pioneer in radiology and discovered radium and polonium
  • First research : tumour or growth treatment using radiation
  • Founder of the Curie Institute (prominent medical research centre)
  • Responsible for The Theory of Radioactivity
  • Passed away due to leukaemia because of direct exposure to radioactivity
• Pierre Curie

  • French chemist and physist
  • Passed away in a road accident in France in 1906
• Ernest Rutherford (1871-1937)

  • Physicist from New Zealand
  • Known as the Father of Nuclear Physics
  • In 1898, when he was investigating absorption of uranium radiation, he found alpha rays and beta rays in uranium radiation
  • He also identified the characteristics of alpha and beta rays
• Radioactive substances

  • Nucleus of an atom comprises of protons and neutrons that is contained by a strong force
  • This strong interaction forms a stable nucleus
  • In average, a medium sized nucleus is more stable than heavy and light nuclei
  • Radioactive substance are elements with unstable nuclei
  • Isotope : element where atoms have the same number of protons but different numbers of neutrons
  • Radioisotopes : Isotopes for radioactive elements
• Element and isotopes

  1. Carbon
  2. Radioisotopes
  3. Carbon-14
  4. Non-Radioisotopes
  5. Carbon-12
  6. Carbon-13
  7. Iodine
  8. Radioisotopes
  9. Iodine-131
  10. Non-Radioisotopes
  11. Iodine-132
  12. Cobalt
  13. Radioisotopes
  14. Cobalt-60
  15. Non-Radioisotopes
  16. Cobalt-59
• Radioactivity or radioactive decay

  • A random and spontaneous decay process to transform an unstable element into stable one by emitting radioactive radiation
  • radioactive radiation
  • Alpha particles (positive radiation)
  • Beta particles (negative radiation)
  • Gamma ray (neutral)
  • Spontaneously - not influenced by physical factors (pressure, temperature, time and others)
  • Definition of spontaneous radioactive decay
  • Decay occurs at uneven time intervals
  • The rate of decay is not the same
  • Example Radioactive elements
  • Carbon-14 (C-14)
  • Radon-222 (Rn-222)
  • Thorium-234 (Th-234)
  • Uranium-238 (U-238)
• Units of Radioactivity

  • Radioactivity can be measured in Becquerel (Bq) and Curie (Ci)
  • Curie (Ci)
  • Measure the rate of unstable nuclei decay or activity in nuclei decay
  • Named in honour of Pierre Curie
  • 1 Ci = 3.7 * 10^10 decay / s
  • 1 Ci is approximately the number of decays per second in 1 g of Radium-226 (Ra-226)
  • Becquerel (Bq)
  • S.I. unit of radioactivity
  • 1 Bq = 1 decay / s
  • named in honour to Henri Becquerel
• Half-life of radioactive decay

  • The activity of radioactive material - rate of decay of the material
  • Depends on the number of atoms that hasn't decayed
  • the activity of radioactive material reduce with time
  • Different radioactive material decay at different rates
  • Rate of decay changes according to the number of radioactive atoms
  • When a radioactive material decays, the
  • Number of decayed atoms increases
  • Number of active atoms decreases
  • Total number of atoms are the same
• Half-life of radioactive decay

  • When a radioactive material decays is not determined but we can determine the time taken by unstable atoms to decay to its original number
  • Half life - time it takes for the nuclei of radioactive material to decay to half the amount of its original amount
  • The half-life for similar radioactive materials are the same but differs for dissimilar radioactive elements
  • Uranium-238 4.5 * 10^9 years
  • Carbon-14 5600 years
  • Torium-234 24 days
  • Iodine-131 8 days
  • Bismuth-214 20 minutes
  • Radon-222 3.8 days
• Half-life of radioactive decay

  • Information of half-life of certain radioactive materials is essential especially in medical field
  • Radioactive element used in medical field have a short half-life as to avoid over-exposure to radiation to patients for a long period of time
  • Example
  • Technetium-99 (Te-99) that a half life 6 hours is injected into patient's blood to detect brain cancer, internal bleeding and blooding clotting
  • After one day, technetium-99 will reduce to 62.5% from its original value and will not harm the patients
• Radioactive detector

  • Radiation that is exposed to the air will ionise air molecules
  • The ionising power of the three radioactive rays are different
  • All the radioactive detectors except the photography disc function based on ionisations of radiation
  • Example of radioactive detectors
  • Geiger-Muller tube
  • Cloud chamber
  • Scintillator counter
  • Electroscope
  • Photography disc
• Cloud chamber

  • The cloud chamber is made of a transparent plastic box
  • The chamber is divided into two portions by using metal discs
  • The bottom part is filled with solid carbon dioxide
  • A sponge is used to press carbon dioxide onto a metal disc
  • Upper part is filled with alcohol molecules that is released from cloth dipped in alcohol
  • Alcohol vapour becomes cold when it seeps down and creates a saturated space at the bottom of the chamber and is suitable for condensation

  
• Cloud chamber

  • When a radiation enters the chamber, ionisation of air occurs
  • The saturated alcohol vapour moves towards the ions and is condensed
  • Alcohol drops on the iron will create radioactive traces
• Get clearer traces in cloud chamber

  • The transparent perspex cover should be scrubbed with a soft cloth to produce charges that will discharge the ions in the chamber before the radiation enters
  • The cloud chamber is put horizontally to ensure all particles in it move smoothly
  • If light is used, the rays should be shone upon the most saturated space with alcohol molecules and not on the black disc to avoid heating up the disc