Nucleus - 2

Nuclear Fusion:-
the process of combining two light nuclei to form a heavy nucleus is known as nuclear fusion
when two light nuclei (having low binding energy the nucleon)are combined to form a heavy nucleus there
occurs a small mass defect which gets converted in to energy
eg:
process requires very high temperature for occurnce.

Dumb question:
why such a high temperature necessary?
Ans: This is because when possitively changed nuclei come close to each other for Fusion they required very high energy to counter replusive
force between them.
[illustration] Two determine nuclei fuse to form a tritium nucleus and a proton as by product . compute the energy released.
given: Mass of deterium=2.01414
Mass of tritium nucleus=3.01605u
and mass of proton=1.00782u
[solution]

mass of reactants = 2.0141 x 2 = 4.028204
mass of products=3.01602 + 1.00782=4.02387u
mass defect = 4.0282 - 4.02387 = 0.00433u
Energy released = 000433 X 931 = 4.03 Mev

Dumb Question:
how has the factor 931 come in computation?
Ans: E = mc², if mass is 1amu
and it is converted in to energy by this relation then
E = 931 Mev
1u mass defect is equivalent to931Mev of energy produced

Radioactivity: the phenomenon of sportaneous emission of radiation from radioactive substance is known as Radioactivity.
This is exhibited naturally by certain heavy elements like uranium,Radium, thorium etc. Few radioactivity decay are:
- decay: in this case an particle(helium nuclus) is ejected and parent nucle looses two protons and two neutrons

- decay: in this process change Ze of nucleus changes but the number of nucleons remin unchanged. This happens if
nucleus emits an electron(^- decay) or positron.
In this process either protons is converted in to neutron or vice-versa (₊ decay) is also accompained by release of a changeless
and massless particle called neutrino
decay: a gamma ray emmision does not affect either the change or number

Radioactive Law
In a typical decay process, unstable nucleus (parent0 decays and results in the formation of daughter. Thus effectively no. of parent nucleus decress in the process.
If initially there were N₀ unstable nucleus, then after time t, the no. of parent nucleus N remaining is given by
N = N₀ where decay constant.
This law is followed by all radioactive decays
• The time Required to get the number of parents nuclei halved is given by

• Another quantity that measure the rapidity of decay is the average or mean life time of a nucleus,
t_av is given by

Average life=1.44 times the half life

why??