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Uranium ores contain one radium `-226` atom for every `2.8 xx 106` uranium `-238` atoms. Calculate the half-life of `._92 U6238` given that the half-life of `._88 Ra^226` is `1600` years `(._88Ra^226` is a decay product of `._92 U^238`) :A. `1.75 xx 10^3 years`B. `1600 xx (238)/(92) years`C. `4.5 xx 10^9 years`D. `1600 years` |
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Answer» Correct Answer - C ( c) `N_1 lamda_1 = N_2 lamda_2` `T = (0.693)/(lamda)` Hence `2.8 xx 10^6 xx (0.693)/(T_1(U)) = 1 xx (0.693)/(T_2 (Ra))` `:. T_1 (U) = 1600 xx 2.8 xx 10^6` `=4.48 xx 10^9` years `~~ 4.5 xx 10^9` years. |
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