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gcse science P4 - G
specific for ocr gateway additonal science B.
Question | Answer |
---|---|
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 |