Half life of a certain radioactive material is 130 days. After what lapse of time, the undecayed fraction of the material will be 25% ?

Half life of a certain radioactive material is 140 days. After what lapse of time, the undecayed fraction of the material will be 25% ?

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

A certain radioactive material is known to decay at a rate proportional to the amount present. Initially there is 50 kg of the material present and after 2h it is observed that the material has lost 10% of its original mass. Based on these data answer the following questions. The time at which the material has decayed to one half of its initial mass is

A radioactive sample decays by simultaneous emission of two particles having respective half-lives of 1,620 years and 810 years. After what time, one fourth of the sample will be left behind?

The half-life of a radioactive substance is 1,672 years. If the initial mass of the substance is 1 g, after how many years will only 1 mg of it to be left behind?

The helf life period o a radioactive substace is 30 days.What is the time taken for 3//4th of its original mass to disintegrate?