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1.

The isotopes `.^(238)U` and `.^(235)U` occur in nature in the mass ratio 140 : 1. it is assumed that intially they were found in equal mass. If half life `(t_(1//2))` of `.^(238)U=4.5xx10^(9)` and `t_(1//2)` of `.^(235)Uxx10^(8)` years respectively then the age of earth is `(log 7=0.846,log2=0.3)`A. `4.02xx10^(9)` yearB. `2.01xx10^(9)` yearC. `8.72xx10^(9)` yearD. none of these

Answer» Correct Answer - A
Discussion
2.

Alpha decay of `._(92)^(238)U` forms `._(90)^(234)Th`. What kind of decay from `._(90)^(234)Th` produces `._(84)^(234)Ac` ?A. `alpha`B. `beta`C. `beta^(+)`(positron)D. `gamma` -emission

Answer» Correct Answer - C
Discussion