# Dual nature of light

1. Jan 16, 2012

### bobsmith76

In the documentary the Fabric of the Cosmos Leonard Susskind remarks how confused he is that a photon could be both a wave and a particle, he says a rock is a rock, and a wave is a wave (a picture of an ocean wave crashing). How could a rock be a wave?

To me the answer is obvious, a wave is just an abstract description of how matter moves. Any material body can be both a body and a wave so long as it moves in a wave form. I don't understand why this is hard to understand.

I put this in the classical category because it concerns optics.

2. Jan 16, 2012

### Staff: Mentor

Susskind is making the point that there is no true wave-particle dichotomy. His confusion is rhetorical.

3. Jan 17, 2012

### lavinia

In Maxwell's equations, light is a traveling pair of orthogonal waves, one an electric field, the other a magnetic field. This description does not use the idea of motion of matter. Rather it uses the idea of oscillating fields.

Many fields - e.g. the static gravitational field or static electric field - can be thought of as mere mathematical conveniences for describing a distribution of forces in space. They are a way to avoid discussing action at a distance. But the electromagnetic field describes light itself and in some sense is not just a convenience. So this is a case where the wave is niether a description of motion of matter not is it a pure mathematical convenience.

4. Jan 17, 2012

### Drakkith

Staff Emeritus
A wave in water is easy to understand because there are untold trillions and trillions of atoms that contribute to the effect. However with single particles this is not the case. There is no way to understand it other than to accept that the math used to describe, understand, and predict where something will be is a wavefunction.

Personally I choose to view it like this. All "particle" and "wave" like properties that are observable to us in our everyday lives, are simply a likeness of the actual quantum effect which is the "real" way the universe works. So a water wave uses similar math and acts similar to the "quantum" effect, but only so far. A water wave will not tunnel to the other side of a barrier like a subatomic particle can. But I'm sure I've broken a dozen scientific rules or something with this.