1. The half life of a certain radioactive material against α-decay is 100 days. After how much time, will the undecayed fraction of the material be 6·25%.
2. Let at time t = 0 number of atoms in radioactive element is N0. At time‘t’ , number of undecayed atoms N , then
3. Correct relation between half life T½ and Decay constant \(\lambda\)
4. How long will a radioactive isotope, whose half life is T years, take for its activity to reduce to 1/8th of its initial value?
5. Rate of disintegration is also known as
6. Mean or average life of a raioactive sample is _________________ decay constant.
7. Spontaneous disintegration of a heavy nulei is known as
8. Reciprocal of time during which the number of atoms of a radioactive substance falls to 1/e or 37% of original number of atoms presents is known as
9. For the decay to take place, the mass of the parent nucleus must be ____________ the total mass of the decay products.
10. SI unit of activity is