[Foobarz]

Ok, so here's something I'm not getting about the De Broglie equation

If (lambda)= h/mv then how come there are different wavelengths of light? Shouldn't the mass of the photon remain constant and the speed of light is a constant 3.00*10^8 m/s? Why are there then different wavelenghts?

[CrimpJiggler]

I found this:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/960731.html
I don't understand it myself. How can something with no mass have momentum?

[Foobarz]

LOL AGREED
I don't get why we're learning this theoretical physics stuff in my AP Chem class. I understand learning about electrons and bonding, but I don't get how the wave properties of electrons relate to chemistry. . .

[vmelkon]

I imagine it is because a photon can't be stopped. The speed can be reduced a little bit if it passes through something with a certain index of refraction, but that is a special phenomenon.  Also, the speed remains constant even in the object with a certain index of refraction.
You won't be able to reduce the speed to 1 m/s or anything really low. Therefore, it doesn't have a mass.

Also, light passes through itself. There is no such thing as a head on photon-photon collision.

There probably are better explanations in physics books.

[Borek]

If (lambda)= h/mv then how come there are different wavelengths of light?

Photon is massless and is not described by De Broglie equation.

How can something with no mass have momentum?

Don't try to follow classic physics intuitions in the quantum world. They are rarely helpful.

I understand learning about electrons and bonding, but I don't get how the wave properties of electrons relate to chemistry...

Wave properties of the electron are responsible for the way orbitals are shaped, so there is a strong connection.

[Foobarz]

Thank you Borek now I understand the differentiation between classical mechanics and quantum mechanics.

[CrimpJiggler]

LOL AGREED
I don't get why we're learning this theoretical physics stuff in my AP Chem class. I understand learning about electrons and bonding, but I don't get how the wave properties of electrons relate to chemistry. . .

Couldn't agree with you more on that one. They flood you with all this theory but leave out the practical applications. It doesn't work for me, I learn by solving problems and putting knowledge into practice. If I can't put it into practice I can't see the point in learning it. I'm in my 3rd year of a chemistry course in uni now and I have to admit that I'm regularly glad that I learned a lot of the theory I resisted in the past cuz it paves the way to understanding all sorts of chemistry concepts. For example MO theory. I used to think it was purely theoretical bulls&$# but now that I know it I can understand things about spectroscopy that I wouldn't be able to without knowing MO theory.