Background Radiation | Physics for GCSE/IGCSE - Year 11 PDF Download

Background Radiation

• It is crucial to understand that radiation is a natural occurrence
• Radioactive elements have always been present on Earth and in outer space
• Human activities have contributed to the radiation exposure levels on Earth
• Background radiation is described as:
  • The continuous radiation present in our surroundings
• There exist two categories of background radiation:
  • Natural sources
  • Man-made sources

Background radiation is the radiation that is present all around in the environment. Radon gas is given off from some types of rock

• Natural Sources of Radiation

  • Rocks: Certain types of rocks emit radiation.
  • Cosmic Rays from Space: Radiation from outer space contributes to background radiation.
  • Foods: Some foods naturally contain radioactive elements.
• While most background radiation originates from natural sources, a small portion stems from artificial sources like medical procedures, including X-rays.
• The levels of background radiation can vary significantly depending on the geographical location.

Sources of Background Radiation

• Background radiation can originate from natural sources on Earth or in space as well as from human-made sources.

Natural Sources

Radon Gas in the Air

• Airborne radon is produced from the ground due to the natural decay of uranium found in rocks and soil.
• Radon gas is tasteless, colorless, and odorless, although it is generally not considered a significant health concern.

Radioactive Elements in Rocks and Buildings

• Heavy radioactive elements like uranium and thorium exist naturally in rocks underground.
• Uranium undergoes decay, transforming into radon gas, known as an alpha emitter.
• Inhalation of radon gas in significant amounts can be particularly hazardous to the lungs.
• Natural radioactivity is present in building materials such as decorative rocks, stone, and brick.

Cosmic Rays from Space

• The sun constantly releases a vast number of protons, some of which penetrate the Earth's atmosphere at high velocities.
• Collision of these protons with air molecules results in the generation of gamma radiation.
• Other sources of cosmic rays include supernovae and high-energy cosmic events.

Carbon-14 in Biological Material

• All organic matter contains a minute quantity of carbon-14.
• Living organisms continuously replenish carbon in their systems, maintaining a relatively stable amount of carbon-14.

Radioactive Material in Food and Drink

• Naturally occurring radioactive elements can infiltrate food and water due to their presence in rocks and soil.
• Some foods, like bananas containing potassium-40, have higher concentrations of radioactive materials.
• However, the levels of radioactive substances in food and drink are negligible and do not pose significant risks.

Man-Made Sources

Medical Uses of Radiation

• Radiation is commonly used in medicine for various purposes such as X-rays, CT scans, radioactive tracers, and radiation therapy.
• It plays a crucial role in diagnosing and treating medical conditions effectively.

Nuclear Waste and Fallout

• Nuclear waste, though not a major contributor to background radiation, can be hazardous for individuals handling it.
• Fallout, the radioactive residue from nuclear explosions like in Hiroshima, poses risks in areas where nuclear testing occurs.

Nuclear Accidents

• Incidents like the Chernobyl disaster release large amounts of radiation into the environment, leading to severe consequences.
• While rare, nuclear accidents can have devastating long-term effects on affected regions.

Detection of Radiation

• Regulating human exposure to radiation is crucial to prevent harmful effects.
• The measure of radiation a person receives is termed the dose.
• Ionizing nuclear radiation is typically quantified using a detector connected to a counter.

Count Rate

• Count rate refers to the number of decays per second detected by a radiation detector and recorded by a counter.
• It is typically measured in counts per second (counts/s) or counts per minute (counts/min).
• The count rate decreases as the detector moves further away from the radiation source. This is because the radiation becomes more dispersed with distance.

Geiger-Müller Tube

• The Geiger-Müller tube is a commonly used device for detecting and measuring radiation levels.
• Each time the tube absorbs radiation, it sends an electrical pulse to a counting machine, resulting in a clicking sound or display of the count rate.
• The frequency of clicks or the count rate directly correlates with the amount of radiation absorbed by the tube. Higher counts indicate more radiation exposure.
• The proximity of the tube to the radiation source affects the count rate; the further away from the source, the lower the count rate detected.

Other Radiation Detectors

• Photographic Film: Often utilized in badges for radiation detection.
• Ionisation Chambers
• Scintillation Counters
• Spark Counters

Accounting for Background Radiation

• Background radiation needs to be considered when taking measurements in a laboratory.
• To account for background radiation, readings are taken without a radioactive source and then subtracted from readings with the source, giving us the corrected count rate.