Activity and half life

• Count rate is the number of radioactive nuclei.
• Activity is the number of unstable nuclei in the source that decay per second.
• The decay of a radioisotope is a random event.
• Both contamination and irradiation are potentially hazardous, but also have useful applications to everyday life.
• Irradiation is the process where something has been exposed to a radioactive material.
• Contamination is when something radioactive has got somewhere it should not be.
• It is possible to predict with a high degree of probability the average rate of decay for a large number of nuclei within a given sample.
• The rate of decay for each type of radioactive isotope is a constant and is a characteristic of that given isotope.
• Half Life is the time taken for half the radioactive atoms to decay.
• The time radioactivity takes to reach half its dose is known as Half Life.
• Half-life is the average time taken for number of unstable nuclei to halve.
• The half-life for the model isotope can be calculated.
• The dice represent the number of unstable nuclei present.
• The dice with the number 5 face up represent the count rate.
• It was possible to predict the rate of decay.
• A graph of number of unstable nuclei against time can be plotted.
• The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in the sample to halve.
• A Geiger-Müller tube is used to record the activity of a sample over a period of time.
• Contamination is when something radioactive gets into a place we don’t want it.
• Shroud of Turin
• Irradiation is being exposed to a radioactive source.
• Contamination is also useful.
• You can detect the radiation from a tracer and create an image of what that organ looks like, for example, the lungs.
• The time it takes for the count rate from a sample containing the isotope to fall to half its initial value is also the half-life of the isotope.
• Irradiation also lengthens the shelf life of fruit.
• We sometimes use radiation to steralize equipment by killing off the bacteria.
• The count rate of your element is unaffected when paper is placed between the source and the Geiger–Müller tube, but drops to almost zero when 5 mm aluminium is used.
• Irradiation is not always a bad thing.
• Carbon 14 is radioactive, so by looking how much carbon 14 is left in the material we can calculate how many half lives have occurred, therefore how old it is.
• Carbon 14 is produced in the atmosphere, so anything that is alive or has been alive contains it.
• Radioactive decay is a random process, you cannot predict when a nucleus will decay or which nucleus will decay.
• Step 1: Half the original count rate / activity.
• The half life of the graph can be determined by drawing a line across from the value from step 1 and down to the time.
• The half life of the graph can be determined by drawing a line
• If 10% of unstable atoms decay every hour, the number of unstable nuclei present after seven hours can be calculated using the formula: Number of unstable nuclei after n half-lives = initial count rate / 2.
• Half life is the average time that it takes for the level of radiation to fall by half.
• Step 2: Draw a line across from the value from step 1 and down to the time.
• A particular radioactive isotope has a half-life of 6.0 hours and a sample of this isotope contains 60 000 radioactive nuclei.
• The number of radioactive nuclei after 24 hours can be calculated using the formula: n = 4 (24/6=4) and the initial count rate is 60 000 / 16 = 3750.
• Half life graphs can be used to determine the half life of a radioactive isotope.