The shape of light

[swansont]

Perhaps consider a photon as an envelope with a fuzzy outline. Its shape depends upon your power of resolution? (How far from the theoretical "centre" you measure its peripheral uncertainty effects). From the side, would it not look like a sort of sinusoidal envelope whose length depends upon observation time?

 

You can only "observe" a photon by interacting with it.

[SmallIsPower]

Unfortunately, most "slow light" in reality is slow because it's absorbed, released and bouncing around, when the photon exists, it's moving at lightspeed, but not neccarsarily in the straight line that gets measured.

[chitrangda]

light travels in straight line. when u see any straight object from front u can c it where as the angle change with side viewing

simmilar is the case with light.

[cpwmatthews]

i'd rather read little an imagine lots, I agree that light may be multidimetionable thus allowing it to go everywhere and that a beam only exhists because it is focused in that direction but it interesting to thnk it can be quantified

[timo]

At some point you should ask yourself what light or a photon actually is. For what light is, I cannot really give you a good answer so let´s stick to the photons and start from the very basics:

There is something called the "electromagnetic field". Being a field, that means that it is a function that has a certain value (not nessecarily a real- or complex-valued one, it can also be vectors, tensors or even anything else) on every point of space(-time). To some extend, this field is all there is if you ignore that you want field equations, interaction of this field with matter/other fields and at some point also quantization of the field. Think of it as the surface of the ocean. If you assign a water-height to every point of the ocean-surface, you have completely described it. Field equations would be something like the time-evolution of waves, interaction with other matter would be the wind blowing on and creating waves, .... let´s ignore quantization .

 

The height-field of the water is a function f: R² x R -> R ("x R" for time). You can easily compose it as a sum of different functions: f = f1 + f2 + ... .This can be handy, e.g. if you are a surfer. As a surfer, you are not interested in the height of the water at any point, but in the waves rolling towards the beach. So you would compose the field of functions which each represent some object that makes sense for your application (surfing): An object you intuitively call a wave. If you´re rather interested in the moon causing tides, you´d probably take different functions to make up the height-field f. So the choice of these f_i is pretty much arbitrary as they are just some helper-functions that simplify calculations (timing in the case of surfing).

To get the connection to photons: They are basically such basic components of the electromagnetic field and therefore their choice is arbitrary to some degree and depends on what you are actually interested in. So the shape of a photon is exactly the shape that you assign to it, the most common choice being a plane wave (for being an eigenstate to the momentum operator).

[gcol]

. So the shape of a photon is exactly the shape that you assign to it,

 

Could you put that another way, such as "The shape of light depends upon which parameter and property you are considering, and the range at which you are considering it?"

 

Tell me the shape you want, and I will choose the parameters that achieve it.