# Quantum physics

1. Mar 3, 2009

### killer120

then i want to know how to prove E=hf without any assumption but with our basic physics knowledge to prove the formula is actually explaining quantum physics theory.................i still blur about the formula for quantum physics...thanks if someone help me out!

2. Mar 3, 2009

### humanino

In principle, you could "derive" it from other stuff, either using a Shrodinger-like equation, or a correspondance principle + symmetry arguments "a la Noether"... well. But I think that would not be fair. The formula was taken as an assumption, then we built a lot of stuff considering it correct, then we come up with 20-50 years of theoretical deepening, quantum gauge fields etc... and then we can come back and claim to derive $E=h\nu$. Looks pretty much like cheating to me... Are you researching something new in the foundation of quantum mechanics ?

3. Mar 3, 2009

### The Bob

The formula, as my understanding goes, was derived from experimentation. It is like a physics axiom. I have done this experiment myself and I found h to a good number of decimal places. I can't think of a way to derive it from classical physics though. Will have a think and probably realise it was simple all along.

The Bob

4. Mar 4, 2009

### arunma

The equation E = hf can be empirically deduced for light waves with a simple photoelectric experiment. I think I even did it once back in college. In the context of quantum mechanics, this is taken as an assumption in the case of matter waves. Basically we just assume that matter waves behave like light waves. And from this, as well as the de Broglie relation, we get the Schrodinger Equation and all of quantum mechanics.

5. Mar 5, 2009

### neu

Simple:

$$E=hc/\lambda$$
$$c=\nu\lambda$$
so $$E=h\nu$$

6. Mar 6, 2009

### map19

Planck derived his constant from experiment, as described here: - http://en.wikipedia.org/wiki/Planck's_constant

Some other constants and formulae we use in physics have not yet been deduced from first priciples.
Newton's laws.
Maxwell's equations.
The Schrodinger equation.