Half life of a radioactive substance is 15 seconds. After 15 seconds what percentage of activity will be left ?

Half-life period of a substance is 20 days. After 30 days what percentage of the substance will be left.

The half life period of a radioactive substance is 15 minutes. What per cent of radioactivity of that material will remain after 45 minutes ?

The half-life of a radioactive substance is 1 y. After 2 y, what will the amount of the substance that will be disintegrated?

The half life period of a radioactive element is 90 minutes. What percentage of radioactive element will be present after 6 hours of decomposition ?

The half life period of a radio active material is 15 minutes. What percentage of radioactivity of that material will remain after 45 minutes ?

The decay constant of a radioactive substance is 1 per month. The percentage of radioactive substance left undecayed after two months will be