Question

What is quantum physics & why is it used?

Answer 1

quantum physics is also known as quantum mechanics which deals with fundamental theory of nature at small scale and low energies of atom and its particles.
its use in atomic structure jumping of atom from their energies level and also atomic clock and in frequency too

Answer 2

quantum physics is related to mprden physics .e.g structure of atom.
plank quantum theory ,within this physics
plank quantum theory :-
according to plank, energy associated with electrons in just like package .( named as quanta ) .
E =hv
where E is the energy of one photon or quanta , h is plank constant and v is the frequency of photon .

in atomic quantum physics is very important to explain structure of atom .
according to this concept there are four quantum number exist for definig of electrons position .
(a) principal quantum number
(b) azimuthal quantum number
(c) magnetic quantum number
(e)spin quantum number