1. What is nucleus?

It is the part of an atom where whole mass of the atom is
assume to be concentrated.Or it is the central part of an
atom which contain proton and nuetron.

2. How is energy transformed in windmills?

Essentially what happens is that as the energy from the
wind rotates the vanes of the mill, coils of wire rotate
inside a permanent magnet (generator) and produce electric
voltage/current. This current is then sent onto the grid
and used by us as electricity another form of energy. This
is a very simple explanation and there is a lot more in the
design of the system.

4. In radioactive dating we use half life to determine the age of a sample but not average life why?

It is a quantitative measure in which we compare the
quantity of a radioactive substance in the sample to that
in the atmosphere/fresh substance.

5. What is meant by the rest mass energy of an electron?

According to the Einstein's Theory of Relativity, the mass
of a body (say a particle) depends on the energy and on the
momentum (say the velocity) with which the particle moves.
So, we have a problem: is there a mass value that every
observers can relate to? Yes: is the rest mass, that is the
mass you could measure in a frame of reference co-moving
with the particle (in which the particle is still), that is
the center-of-mass frame and that coincide with the minimum
value measurable for every observers.

6. What is fussion?

It is a nuclear reaction in which two nuclei combine to
form a larger (with nearly combined mass) nuclei.
It releases lot of energy.
Sun and stars release energy in this fashion

7. What is the difference between cathode ray and beta ray?

acctualy normal on the wave front called RAY, in the beta
radiation there is wave packet and hence no wave frant. in
cathod ray there is electromegnatic radiation and we can
use word ray but in the case of beta partical we use word
beta radiation insted of betaray

8. Can an electron be obtained (or come out) from the nucleus?

Yes, electron having an energy higher than the ordinary
atomic electron may come out of the nucleus due to beta
decay process. A negative beta is identical to an electron
in all respect except with difference in kinetic energy.

9. Explain history of nuclear reaction?

bigger nuclues broken to from two lighter nucleus and two or
three neutrons is called nuclear fission used for making
atom bomb
two ligther nucleus joined to form bigger nucleus is called
nuclear fussion used for making hydrogen bomb

10. What is Fission and Fusion?

Fission: The breaking down of a Nucleus (not atom) into
smaller nuclei. It is usually induced by a neutron.
For example, a Helium nucleus (called alpha particle) is
divided into two 4He(+2) --> 2H(+1) + 2H(+1)
A lot of enery is released in the process.

Fusion: This happens when two nuclei combines to form a
larger nuclei. Huge amount of enery is needed to start
this. Because its not easy to bring two positively charged
nuclei closer.
When they combine, a huge amount of energy is released.
This usually happens in the stars.
The enery required to start the fusion comes from the
gravitational force between the particles.