A 280 days old radioactive substance shows an activity of 6000 dps. 140 days later, its activity becomes 3000 dps. What was its initial activity? [2004]

Question

A 280 days old radioactive substance shows an activity of 6000 dps. 140 days later, its activity becomes 3000 dps. What was its initial activity? [2004]

Smart Achievers · Accepted Answer

(2)

In two half lives, the activity will remain $\frac{1}{4}$ of its initial activity.

$∴$ $Initial activity = 4 \times 6000 = 24000 dps$

Solution

Q.
A 280 days old radioactive substance shows an activity of 6000 dps. 140 days later, its activity becomes 3000 dps. What was its initial activity [2004]

1 20000 dps

2 24000 dps

3 12000 dps

4 6000 dps

Ans.
(2)

In two half lives, the activity will remain $\frac{1}{4}$ of its initial activity.

$∴$ $Initial activity = 4 \times 6000 = 24000 dps$

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