Question

The half life of a radioactive material is 8 hours. Its 20% fraction remains active after time t. Its 10% fraction will remain active after- (1) (t + 2) hours (2) (t + 4) hours (3) (t + 6) hours (4) (t + 8) hours​

Answer 1

$\huge\bigstar\underline\pink{Answer}$

★ Question seems to be horrible but it's very easy , you don't even have to use your pen.

★ To decay upto 20% , time taken =t

★ To decay from 20% to 10% time taken = half life = 8hr

★ so, total time taken = T = (t+8)

Option 4 is correct ✔️✔️

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