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 certain radioactive substance has a half-life period of 30 days. What is the disintegration constant ?

A radioactive isotope has a half-life of T years. The time required for its activity reduced to 6.25% of its original activity

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) Differentiate between half-life and average life of a radioactive substance. (b) A radioactive substance decays for an interval of time equal to its mean life. Find the fraction of the amount of the substance which is left undecayed after this time interval.

_(87)^(221) Ra is a radioactive substance having half life of 4 days .Find the probability that a nucleus undergoes decay after two half lives

A radioactive substance decays to 1//16^(th) of its initial mass in 40 days. The half life of the substance, in days, is :

A radioactive substances decays so that 3% of its initial nuclei remain after 60 seconds. The half life period of the substances is nearly

Half-life of a radioactive substance is 12.5 h and its mass is 256 g . After what time the amount of remaining substance is 1g ?

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

The decay rate of radium at any time t is proportional to its mass at that time. Find the time when the mass will be halved of its initial mass.