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### the quantum world

Posted: Wed Oct 18, 2017 8:45 pm
Can someone explain particle wave duality?

### Re: the quantum world

Posted: Wed Oct 18, 2017 8:53 pm
I've been wondering about this too. It seems that we have to assume that something is both a particle and a wave until we know which one it is? But perhaps this is wrong. An explanation would be wonderful.

### Re: the quantum world  [ENDORSED]

Posted: Thu Oct 19, 2017 2:58 pm
Essentially, electromagnetic radiation can act as both a wave or a particle, depending on the situation. This was shown for example in the photoelectric effect, when the incident UV radiation on the metal acted as photons of light, rather than waves, with each individual photon requiring enough energy to remove one electron. In other experiments, such as in a diffraction experiment, light acted as a wave, constructively and destructively interfering with each other. This resulted in diffraction patterns being present on the screen in areas not directly behind the slits. If light were acting as a particle in this experiment, marks would only be found directly behind the slits, which actually wasn't the case. In the wave model, the intensity of the light is proportional to the amplitude of the wave. In the particle model, intensity is proportional to the number of photons present.

De Broglie suggested that ALL particles can act as waves, and have a wavelength that is dependent upon their momentum. This is where the De Broglie equation comes from.

Hope this helps!

### Re: the quantum world

Posted: Sat Oct 21, 2017 1:10 pm
Particles are thought of as point sources of mass. In math, particularly geometry and calculus, you've probably learned that points are defined as a very specific location on a line or on a plane or surface. They are of zero dimensions and thus have no length, area, or volume; they are just that very precise location and nothing more. Particles then can just be thought of as the mass, among various other properties like electric charge, that is assigned to that point, which again, consists of no space at all. Doing this simplifies calculations enormously; the reason why you've never had to and (hopefully) never will try to dip into quantum mechanics for calculating something like how long it takes the Earth to go around the Sun, calculating how each and every subatomic particle behaves, is because, as classical physicists found out, the particle model produces very simple yet extremely accurate equations for our macroscopic world.

But as we observe smaller and smaller phenomena, classical mechanics no longer works. Through de Broglie's Relation, we know that subatomic particles can be described as waves. And waves, oscillations or disturbances that move through space, are described by their speed and wavelength/frequency, and not by their exact location like with points. Thus, they're probabilistic and give rise to models like the s, p, d, f, etc. orbitals that aren't clear representations of exactly where electrons orbit, but rather areas where they tend to be.

In different circumstances, different models work better.