Half life of `.^(24)Na` is 14.8 hours. In what period of time will a sample of this element lose 90% of its activity?

The half life of ""^(24)Na is 15.0 hours. What percentage of it remains after 60 hours ?

If half-life of a radioactive element is 3 hours. After 9 hours its activity becomes

The half life of .^(212)Pb is 10.6 hour. It undergoes decay to its daughter (unstable) element .^(212)Bi of half life 60.5 minute. Calculate the time at which the daughter element will have maximum activity.

The half-life of ._(6)C^(14) is 5730 years. What fraction of a sample of ._(6)C^(14) will remain unchanged after a period of five half-llves ?

(a) The half life period of radium is 1590 yrs. After how many years will one gram of the pure element, (i)be reduced to one centigram, (ii) lose one centigram. (b) The half life of radon is 3.8 days. After how many days will only one twentieth of radon sample be left over? (c) 1 gm of radioactive substance takes 50 sec. to lose 1 centigram. Find its half life period?

The half-life of the isotope ._11 Na^24 is 15 hrs. How much time does it take for (7)/(8) th of a sample of this isotope to decay ?

The half-life period of a radioactive element is 1.4 xx 10^(10) years. Calculate the time in which the activity of the element is reduced to 90% of its original value.