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gcse science P4 - G

specific for ocr gateway additonal science B.

QuestionAnswer
where does background radiation come from? -radioactive substances from rocks (granite) -cosmic rays from space
where is most background radiation from? natural sources e.g. rocks, cosmic rays, air
where is the rest of background radiation from? human activity e.g. food, medical, nucleur power, nucleur weapons testing
what are tracers used for? -to track the dispersal of waste materials -to find leaks or blockages in underground pipes -to track the route of underground pipes
what happens when using a tracer to locate a leak in an underground pipe? -a very small amount of a gamma emitter is put into the pipe -a detector is passed along the ground above the pipe -an increase in activity is detected in the region of the leak -little or no activity is detected after this point
what type of rocks contain traces of uranium? granite
what is uranium? a radioactive material
what happens to the uranium isotopes in the rocks? -they go through a series of decays -this eventually forms a stable isotope of lead
how can you find the age of a rock? by comparing the amounts of uranium and lead present in the rock
what is the half life of uranium-238? 4500 million years
what is the atomic mass and atomic number of lead? 206 Pb (stable) 82
what happens to the proportion of lead as time increases? also increases
how can you tell if a rock is 4500 million years (one half-life) old? if there are equal quantities of 238 206 U and Pb 92 82
what is carbon-14? a radioactive isotope which is present in all living things
how can you find the age? by measuring the amount of carbon-14 in an archaeology find
what happens when an object dies? no more carbon-14 is produced
what happens as carbon-14 decays? the activity of the sample decreases
what leads to a reasonably accurate date? the ratio of current activity from living matter, to the sample activity
Created by: jirwin
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