Home / Aptitude Tests / Physics / A piece of radioacti...

A piece of radioactive material contains 10\(^{20}\) atom...

A piece of radioactive material contains 10\(^{20}\) atoms.
If the half life of the material is 20 seconds, the number of disintegration in the first second is?

A.

3.47 x 1018

B.

6.93 x 10 20

C.

3.47 x 1020

D.

6.93 x 1018

Correct answer is A

The number of disintegration,∆N in time interval At, is given by
- ∆N = N∆t
Where N is the number of atoms present at the time t
But ^ = (0.693)/T

= 0.693 ÷ 20

= 0.0347
∴ ∆N = 0.0347 \(\times\) 10\(^20\)

= 3.47 \(\times\) 10\(^18\)