CBSE Class 12science  Radioactivity Videos
Radioactivity  Part 1
This video explains the process of radioactivity in detail.
 55Cs124(Z=55,A=124) has a half life of 30.8s. (a) If we have 7.8 microgram initially, how many nuclei are presents? How many are present 2 min later? (b) What is the activity at this time? (c) After how much time will the activity drop to less than about 1 per second?

how are we supposed to solve this question
 Carbon14(C14) decays at a constant rate in such a way that it reduces to 50% in 5568 years. Find the age of an old wooden piece in which the carbon is only 25% of the original.

Radioactive nuclei

Radioactive elements
 Halflife period of a radioactive sample is 2 days. If the number of nuclei initially present is, find the number of nuclei present after 8 days?
 figure for 13.6 in chapter nuclei
 The half life period of a radioactive substance is 30 days. What is the time for Â¾ th of its original mass to disintegrate?
 How many α and βpartiles are emitted _{90}Th^{232} changes to _{82}Pb^{208}?
 Complete the following nuclear reactions (a) 4B_{e}^{9} + _{1}H^{1} →3L_{i}^{6} + ................ (b) 5B^{10} + → + ..............