23.3 Using radioisotopes Medical uses  To treat certain types of cancers.  For example: Iodine-131: to treat cancers in the thyroid gland High-energy  radiation: cobalt-60 is used as the source of  radiation in hospitals Radiotherapy

23.3 Using radioisotopes Medical tracers A radioisotope is injected into a patient’s body. The tracers injected travels to the organs.  For example, technetium-99 is used to diagnose problems in the bones, liver, kidneys and digestive systems. Images of the organ are taken by a gamma camera.

23.3 Using radioisotopes  Not too long  reduce patient’s exposure to radiation  Not too short  radiation level is more stable Why is a  - emitting tracer used?   radiation can penetrate through the body tissue easily and causes little ionization in the body. How should we decide the half-life of the tracer?

23.3 Using radioisotopes Industrial uses  To control the thickness of paper, plastic or aluminium sheets during manufacture. Thickness gauges plastic sheet source of  radiation detector control circuits equipment to adjust the position of roller movable roller fixed roller

23.3 Using radioisotopes If the sheet is too thin,If the sheet is too thick, The sheet absorbs less radiation. More radiation reaches the detector. The sheet absorbs more radiation. Less radiation reaches the detector. Control the pressure on the rollers, and keep the thickness of the sheet constant.

23.3 Using radioisotopes  To detect pipe leaks. Industrial tracers underground oil pipe Small amount of radioisotopes are often added to oil pipelines. A higher level of radiation is detected at where leakage occurs.

23.3 Using radioisotopes   radiation from radioisotopes is used to look for flaws in metal. Detecting flaws  radiation passes through metal The radiation is detected on a photographic film. Any flaws in the metal of bridges and building frames can be discovered from the image.

23.3 Using radioisotopes Use in scientific research  To find the ages of fossils and the remains of plants or animals. Carbon-14 dating carbon-12 (abundant and stable) carbon-14 (scarce and radioactive) Carbon in Earth’s atmosphere living organisms exchange carbon with atmosphere. amount of carbon-14 in the body = that in the air

23.3 Using radioisotopes The activity of the carbon-14 in remains is halved every 5700 years. organisms die amount of carbon-14 in the body decreases through radioactive decay B.C B.C B.C B.C A.D.

23.3 Using radioisotopes  It has an uncertainty of about 15% due to variation of carbon-14 in the atmosphere through the centuries. How accurate is carbon-14 dating? Any restrictions on carbon- 14 dating?  It cannot be used to date objects older than years.  Other methods using radioisotopes of uranium are used instead.

23.3 Using radioisotopes That’s the end of Section 23.3 Check Point Key Ideas Previous Page Section 23.4 Exit