Question

What quantum is and use for?

Answer 1

Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems

Go here for more information: http://en.wikipedia.org/wiki/Quantum_chemistry
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Answer 2

In quantum theory it is said that radiant energy emitted from a body is not continuous but discontinuous.The energy come in packets.These packets are called quantum

Answer 3

"Quantum" just means "chunk" and usually it's used to say that something can only come in chunks, not any old quantity. For example, money. As a rule, when you go to the store, the smallest price change is 1 cent. So the grocer could charge you $3.90 for a gallon of milk (390 pennies) or $3.91 (391 pennies) -- but NOT $3.906647 (390.6647 pennies). So price is generally quantized -- price can only change in sudden jumps (quanta) of 1 penny, up or down.

Lots of things are naturally quantized. The number of socks in your drawer, the number of cars in your driveway, the number of your children. Some others aren't, or don't seem so, like the speed of your car on the freeway -- you can drive 60 MPH or 60.0045678 MPH or whatever you like, there doesn't seem to be any limit on how you can change your speed. Your height doesn't seem quantized. You can be 5 feet 2 inches high, or 5 feet 2 and 1/4 inches, or 5 feet 2 and 57/64 inches, and so on. Your weight doesn't seem quantized, and so on.

Two of the most significant scientific advances of the 17th through 20th centuries, the Age of Enlightenment, were atomic theory and quantum mechanics. Atomic theory says that, contrary to what seems to be true, the amount of material in things is quantized. Your weight, for example, actually is quantized. You are made of a certain number of atoms, and your weight can change by the addition of one whole atom, or removing one whole atom -- but it cannot change by the addition of 49/64 of an atom. So your weight, your height -- these things actually are quantized. They just don't seem that way because the smallest possible change, the quantum, is unbelievably tiny, the mass or size of a single atom. Furthermore, chemical change is similarly quantiized -- must always involve a whole number of atoms changing. So the amount of fuel you have in your gas tank, and the amount you can burn to drive a certain distance, must change by a whole number of atoms.

The other advance, quantum mechanics, says that amounts of motion and the energy of motion are also quantized. So, as it turns out, your speed on the highway actually is, generally, quantized -- cannot change except by exceptionally tiny increments. How fast you run when you're trying to catch the bus, the speed of the bus, the force you can exert closing your fingers, the impact of a baseball on a catcher's mitt -- all these things, too, are quantized.

Is there anything left that is NOT quantized? Essentially only one: "spacetime," or more precisely the amount by which you can shift position, or the amount of time that can separate two events. Present theory is that these things are NOT quantized -- can vary by any amount you like. But we also have very strong reasons to think this isn't quite right, that these things probably ought to be quantized, too. We just don't know how to do that yet, and this is the frontier of modern physics, this problem.