What do you mean by half-life of a radioactive substance ?

Define half-life of a radioactive substance.

What is meant by half life of a radioactive substance? Derive expression for them. What is relation between average life and half life?

Define half life of a radioactive substance.

What do you mean by half life period of a radio active substance ?

The activity of a radioactive substance becomes from 8000 Bq to 1000 Bq in 12 days . What is the half-life of the radioactive substance ?

What is meant by the terms of half-life of a radioactive substance and binding energy of a nucleus?