Define Radioactivity of a radioactive substance.

Prove rthat the instantaneous rate of change of the activity of a radioactive substance is inversely propoertional to the square of its half-life.

Define half life of a radioactive substance.

Distinguish between half and average life of a radioactive substance.

Define the term half life period and decay constant of a radioactive substance. Write their SI unit. Establish a relation between them.

define activity of a radioactive material and write its Si units.