classical and quantum physics

plz give some points which can differnatiate classical and quantum physics......
how we are dealing or applying it in our real physics/world

Hi,
I think the major differences are:
*in classical mechanics we deal with no uncertainty, everything is fully determined and exactly determined by the laws.
Also, particles are only particles and waves are only waves, they cannot have dual aspects.
*while in quantum world , we just talk about probability amplitudes , or probablility to have a certain particles at certain position, there is uncertainty in everything.
Also, particles can behave as waves -> they can interfere (Actually this means that their probablity interfere destructively or constructively to have no particles at certain locations and many partciles at others,and inversly waves can behave as particles as in photoelectric effect.
Refards,

tantoun2004 said:

Hi,
I think the major differences are:
*in classical mechanics we deal with no uncertainty, everything is fully determined and exactly determined by the laws.
Also, particles are only particles and waves are only waves, they cannot have dual aspects.
*while in quantum world , we just talk about probability amplitudes , or probablility to have a certain particles at certain position, there is uncertainty in everything.
Also, particles can behave as waves -> they can interfere (Actually this means that their probablity interfere destructively or constructively to have no particles at certain locations and many partciles at others,and inversly waves can behave as particles as in photoelectric effect.
Refards,

Click to expand...

you surely make a good clearence. that is what i am thinking too.

hello tantoun2004

so can we conclude it's only probability that act as line demarcation between classical and quantum mechanics

Hi,
Well we can say that probability if the main difference between classical and quantum physics, other differences are based on the uncertainty based on the fact that everything is probablilistic (as we mentioned interference of probability waves which is called dual aspect...)
But there is another difference that in quantum world everything is quantized , you have a quantum of energy which cannot be subdivided into smaller while in classical mechanics energy can take any value, it forms a continious quantity.

Technically:
*In classical world all laws just give things like : velocity, position , acceleration ,Energy, electric and magnetic field ...All being accurate values and continious as well (can take any value)...Newton's laws of mechanics and maxwell's eqns have no uncertainty.
*While in QM Schrodinger equation(which constitutes the heart of QM) gives us probability wave amplitude, this is the only quantity we can deal with , every other things are derived from it...

On large scale objects QM tends to classical eqns , i.e. uncertainty becomes very very very small , probability amplitude waves become as if they were continious , their sqaure which gives the probabilty become almost = one (Certain event)...
and no need for QM complications while on small scale objects like an electron , QM is a must.

Anyone who tries to apply QM on large scale objects liek a car ...will waste his time and effort and the comutations will not sense the small error , while when dealing with an electron in a lattice you'll get absolutely incorrect result if u don't apply QM.
It's like applying relativity to an object going at 20 m/s !!!!
Regards,

hi,

*i guess a electron studied under quantum mechanics gives a clear view-exhibits
both wave and matter properties-bringin probability into play.
*classical sense some parameters are assumed to be constants but these parameters are not(ex. path of light straight is assumed to constant-but bends under gravity-geodesic and i believe it shld alter the velocity too..if i am right)
*and classical and quantum mechanics has to work together .

now it is time to clarify me
classical physics consists of _______________?
quantum physics consists of _______________?
i mean voltage ,current ,electric field comes under which physics ???? like that

it's really silly to say it comes under both, and it depends on the situation and scale you are dealing with.
i'm not trying to seem vague but it's the truth, and there exists a problem these days on how to make a unified theory of them both. (string theory or m-theory)

you can have some information there:

**broken link removed**