A radioactive substance has a half-life of `h` days. Find a formula for its mass `m` in terms of time `t` if the initial mass is `m_0`. What is its initial decay rate?

A radioactive elements has a half life of 2500 yrs. In how many years will its mass decay by 90% of its initial mass?

A radioactive substance has a half-life of 10 hours. Calculate the activity of 10^(-10) gram of the substance after 2 hours if its atomic mass is 102.

A radioactive substance has a half-life of 64.8 h. A sample containing this isotope has an initial activity (t=0) of 40muCi . Calculate the number of nuclei that decay in the time interval between t_1=10.0h and t_2=12.0h .

(a) A radioactive sample has 6.0 xx 10^(18) active nuclei at a certain instant. How many of these nuclei will still be the same active state after two half-lives? (b) Radioactive phosphours -32 has a half-life of 14 days. A source containing this isotope has an initial activity of 10muCi . (i) What is the activity of the source after 42 days? (ii) What time elapse before the activity of the source falls at 2.5muCi ? (c) 1g of a radioactive substance disintergrates at the rate of 3.7 xx 10^(10) dps . The atomis mass of the substance is 226 . Calculate its mean life.

A radioactive substance has a mass of 16 mg and its half life is 25 years. The quantity of substance will remain to be disintegrated in 100 years is

A radioactive material of mass number 198 decays with half life of 3 days. If initial amount of radioactive material is 2mg then its initial activity will be?

A radioactive sample with half-life 2 days has initial activity 32mu Ci . What will be its activity after 8 days?

If 2.0 g of a radioactive substance has t_(1//2) of 7 days , the half life of 1 g sample is

A radioisotope has a half life of 10 days. If tofay there is 125 g of it left, what was its mass 40 days earlier ?