Light ?

[Dart15]

Hi,

 

Not sure if this is a particle physics, Cosmology or physical science question - maybe all !

 

 

If light travels as a wave, why do the waves not interact with each other (like water waves do) on the way to our eyes. We should surely end up seeing just a mess of light.

 

The question also relates to light sources in the universe where the light has been travelling with/alongside and interacting with other light sources for billions of years. So, how can we see individial (e.g. stars, galaxy's etc) light sources ?

 

Stupid question - obvious answer ?

 

 

George

[Airbrush]

If light travels as a wave, why do the waves not interact with each other (like water waves do) on the way to our eyes. We should surely end up seeing just a mess of light.

 

The question also relates to light sources in the universe where the light has been travelling with/alongside and interacting with other light sources for billions of years. So, how can we see individial (e.g. stars, galaxy's etc) light sources ?

 

Stupid question - obvious answer ?

 

George

 

Not a stupid question to me, nor is the answer obvious. Water waves reach the shore, from thousands of miles away, as distinct waves. They do not end up as a "mess" of waves.

 

I'm not sure about light waves. Anyone else?

[Klaynos]

Interference is what you want to look up. And then probably coherence.

 

They do interact in a way but not in the way you seem to be thinking, but neither do water waves.

 

If you have a wall in water with two holes waves hitting the wall go through the holes and interfere. You still get waves on the.other side though.

[swansont]

IOW, destructive any interference only "gets rid of" a wave at some point. The traveling waves continue on. And there are, in essence, lots of waves because the sources are incoherent. But there is no other interaction between the light as it moves along.

 

In a way, what we do end up seeing is a mess of light.

[Airbrush]

If light travels as a wave, why do the waves not interact with each other (like water waves do) on the way to our eyes. We should surely end up seeing just a mess of light.

 

You are correct that water waves interact, but that interaction does not destroy them as individual waves. Water waves travel in a complex pattern in a wave train. There are a number of waves traveling in a train and they change places like a conveyor belt or an escalator (imagine a conveyor belt of waves traveling on wheels), with each wave of the train, in turn, passing through the other waves in the train, as their individual speeds change.

Edited April 26, 2012 by Airbrush