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1. |
A freshly prepared radioactive source of half-life `2 h` emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source isA. `6 h`B. `12 h`C. `24 h`D. `128 h` |
Answer» Correct Answer - B `64=2^(6)` After `6` half lives activity will become `=(1)/(64)` Hence required time `=6xx2h=12h` |
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