Question

The half life of a radioactive
substance is 7.5 sec. The fraction of
substance left after one minute is
A) 1/128
B) 1/256
C) 1/16
D) 1/64​

Answer 1

Answer:

THE RADIOACTIVE WILL NEVER FINISH IT WILL DECAY IN FRACTIONS SO IN EVERY 7.5 SEC IT WILL BECOME ITS INTIAL HALF OR THE AMOUNT LEFT AFTER DECAY WILL BECOME HALF...

Answer 2

Answer:

The fraction of substance left after one minute is $\frac{1}{256}$

Explanation:

Given that,

The half life of a radioactive substance is 7.5sec

$= > t _{ \frac{1}{2} } = 7.5sec$

Given time period is 1 minute

No.of half-life decays that occur in a minute are

$n = \frac{60}{7.5} = 8$

The fraction of substance left after n decays is given by relation

$f = \frac{1}{2 {}^{n} }$

Substituting our value of n,we get

$f = \frac{1}{2 {}^{8} } = \frac{1}{256}$

Therefore,The fraction of radio active

substance left after one minute is

$\frac{1}{256}$

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