the radioactivity of a sample of cobalt-60 was measured. years later it was found to have 1/8 of the original radioactivity. how many years have passed?

Respuesta :

The half life of cobalt -60 is 5.3 years. And if a half is 5.3 yrs long, then a period of 10.6 years have passed.

How to calculate years in a radioactive sample?

The activity of a radioactive sample is defined as the rate at which radioactive particles are emitted.

After one life, 1/2 the mass of the original isotope remains. After another half life, 1/4 the mass of the original isotope remains

And if a half is 5.3 yrs long, then a period of 10.6 years have passed.

The half life equation is

A(t)  = A0 (1/2) ^ t/t1/2

t1/2 = half life = 5.3 yes

A0 = intial quantity

A(t) = amount left after t years = 1/4 A0

t = time undergone =?

Substitute

1/4 A0 = A0 (1/2) ^ t/5.3

= 1/4 = (1/2) ^ t/5.3

Take the log of

log (1/4) = log { (1/2)^t/5.3}

= log)(1/4) = t/5.3 log (1/2)

Dividend both sides by log (1/2)

log (1/4) / log (1/2) = t/5.3 log(1/2) /log(1/4)

2 = t/5.3

t= 2.53 = 10.6 yrs

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