Quantized energy - Photon

f95toli

This is not correct. Blue light has an enery of around 3 eV, 6eV would be outside the visible par of the spectrum. Again, "quantized" does not mean that the light can only take on values that are integer multiplies of a specific number.

Your equation is the equation for e.g. multi-photon excitation of a transition in an atom.

marksesl

Ok, so a blue photon is just always 3eV. Correct?


"The classical frequency of your light determines the quantization of the photons (as packets of h*nu energy). You can vary the classical frequency of your light continuously, and for every value it takes, you get a different quantized energy for your photons."

So what is the classical frequency of light as opposed to the frequency contained in the photons?

jtbell

The frequency associated with the photon equals the classical frequency of the light that it corresponds to.

The n=3 to n=2 transition in hydrogen produces photons with energy 1.9 eV, frequency f = E/h = 4.59 x 10^14 Hz, and wavelength λ = c/f = 6.53 x 10^-7 m = 653 nm.

If we have a few bazillion of these photons (give or take), we have a classical electromagnetic wave with that frequency and wavelength.

How much is a bazillion? Consider sunlight at the Earth's surface. Hold up a 1 m^2 screen facing directly towards the sun on a clear day, and in one second it will receive about 1500 joules of electromagnetic energy. The light contains all visible wavelengths, of course, but let's pretend it's monochromatic with wavelength 653 nm. Then each photon carries 1.9 eV = 3.04 x 10^-19 J of energy, so one second's worth of light on the screen contains about 1500 / (3.04 x 10^-19) = 4.93 x 10^21 photons.

marksesl

Ok, so a classical electrometric wave is just lots of photons. The frequency of the photons is the same as the classical wave which they make. Now here's the clincher that I've been trying to get straight here for some time. Isn't the wave in a photon essentially a probability wave, or a De Broglie wave? So, does not the everyday characteristics of classical electromagnetic waves: color, focus ability, diffraction, etc. all come from photons’ probability waves?

jtbell

Basically, yes, but the connection is not simple. A large collection of photons with given frequency corresponds to a classical electromagnetic wave with that frequency, but don't fall into the trap of thinking of a photon as a tiny little bundle of classical electric and magnetic fields.

The "photon field" is actually the quantized version of the classical electric potential and magnetic vector potential, which in relativity theory combine to form the "four-potential" A_μ. In quantum field theory, A_μ gets turned into an operator and quantized.

Naty1

I'd say the "The wave 'in a photon' is a physical wave; the probability wave, or wave function, is a probability function consisting of both real and imaginary components..."
but I think these words would/could still be debated today....

I came across nice dynamic illustration and introductory explanation here:

http://en.wikipedia.org/wiki/Wave_function



from

http://arxiv.org/PS_cache/hep-th/pdf/9702/9702027v1.pdf

my adds inside {}....



Also, what we today call Planck's constant started out as the "quantum of action". As usual in science evolution, such discrete interactions were not grandly theorized all at once, and I don't know which led to which, but Planck apparently needed a 'h' factor via the development of
"Classical statistical mechanics which requires the existence of h (but does not define its value)." apparently he was not at all sure any of this was a wise move:


http://en.wikipedia.org/wiki/Plancks_constant



All the while Einstein's 1905 paper on the Photoelectric effect provided further theoretical support:

Heisenberg also utilized the Planck constant in his uncertainty principle [1927] and this became more theoretically developed in the following years.

Exactly what some of the means is still debated/discussed in these forums...a LOT.

Naty1

Here is a different view I finally found in my notes:

psi here the the quantum wave function...of the Schrodinger wave equation....


http://www.physicsforums.com/showthr...=551554&page=2