# The Naked Scientists Forum

### Author Topic: Do light waves travel only in a linear direction?  (Read 2946 times)

#### sithcdw

• Jr. Member
• Posts: 14
##### Do light waves travel only in a linear direction?
« on: 19/05/2010 04:21:10 »
do light waves travel only in a linear direction?
do we only see objects because of the light reflecting off of the material?
what about the "party" lights (the big ones that shine into the sky that can be seen for miles). does  the light have to be reflected off of colloids in the air in order for us to see the light? Otherwise, wouldn't the light beam just travel in a straight trajectory, unseen? If there were no colloids in the air, would we be able to see that light, unless it were directed straight at us?

[MOD EDIT - TITLE ALTERED TO RE-PHRASED IT AS A QUESTION - PLEASE FORMAT YOUR TITLES SIMILARLY IN FUTURE. THANKS.]
« Last Edit: 19/05/2010 08:20:40 by chris »

#### JP

• Neilep Level Member
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##### Re: Do light waves travel only in a linear direction?
« Reply #1 on: 19/05/2010 05:32:18 »
do light waves travel only in a linear direction?
There's a couple of ways to model how light travels: as rays or as waves.  If you're modeling it as rays, then yes, the light rays tend to travel in a straight line unless they hit something.  Their direction changes of course if they encounter something that they bounce off of, or if they encounter a material that causes their speed to change.  Any time their speed changes, rays tend to bend.

You can also think of light as a wave.  It's harder to define a straight line in that case.  Think of throwing a rock into a pond--you see waves coming out in all directions.  Would you say it's moving in a line or not?  In some cases you could think or waves as moving in straight lines.  For example, if you have waves coming straight towards a beach you can say that they're moving in a straight line right towards the beach.  But generally if you want to talk about light moving in straight lines, you want to think about rays.

Quote
do we only see objects because of the light reflecting off of the material?
what about the "party" lights (the big ones that shine into the sky that can be seen for miles). does  the light have to be reflected off of colloids in the air in order for us to see the light? Otherwise, wouldn't the light beam just travel in a straight trajectory, unseen? If there were no colloids in the air, would we be able to see that light, unless it were directed straight at us?
You're exactly right!  For us to see light, it has to reach our eyes.  If you shine a light beam in space where there's nothing for it to bounce off us, you won't see it unless you shine it right into your eyes.

#### lightarrow

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##### Do light waves travel only in a linear direction?
« Reply #2 on: 19/05/2010 15:38:51 »
do light waves travel only in a linear direction?

Actually, it *never* travel in a "linear direction". However, as JP wrote, you can treat light as rays, moving along a straight line, but only within the limits of some precise approximations.

#### The Naked Scientists Forum

##### Do light waves travel only in a linear direction?
« Reply #2 on: 19/05/2010 15:38:51 »