A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is?
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Updated on : 2022-09-05
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Correct option is C)
The number of counts left after time t N=N0(21)t/T1/2 ∴30=240(21)60/T1/2 [∵t=1h=60min] or 24030=(21)60/T1/2 or (21)3=(21)60/T1/2 Comparing the powers, we get ∴T1/260=3 T1/2=360 or T1/2=20min.