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Author Topic: Can lasers be made to curve without a prism?  (Read 2441 times)

Offline thedoc

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Can lasers be made to curve without a prism?
« on: 21/02/2012 16:17:19 »
Can you make a laser spiral or curve without the use of prisms?
Asked by Glyn Edwards, Facebook


                                        Visit the webpage for the podcast in which this question is answered.

 

« Last Edit: 21/02/2012 16:17:19 by _system »


 

Offline thedoc

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Can lasers be made to curve without a prism?
« Reply #1 on: 21/02/2012 16:17:19 »
We answered this question on the show...



Nic -   In free space, the laser has to travel in a straight line.  But as soon as you introduce curving in the medium - so imagine a laser going a liquid crystal cell which had changes in its refractive index as it went through - that would cause it to bend in the same way that a lens could make it bend.
« Last Edit: 21/02/2012 16:17:19 by _system »
 

Offline JP

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Re: Can lasers be made to curve without a prism?
« Reply #2 on: 22/02/2012 02:15:13 »
A cool demo (kitchen science-able, perhaps) is to mix sugar into an aquarium full of cold water and let it sit a while, then shine a laser through it.  You should see the laser bending downward.  This is because the denser, more sugary water settles to the bottom of the tank, which increases the refractive index there. There's a writeup with pictures on the Buffalo State website: http://physicsed.buffalostate.edu/pubs/StudentIndepStudy/EURP09/Sugar/sugar.html
 

Offline Geezer

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Re: Can lasers be made to curve without a prism?
« Reply #3 on: 22/02/2012 05:08:04 »
Doesn't gravity do the bendy thing too, or is that because it bends space so that really the "laser" beam is still traveling in a straight line?
 

Offline yor_on

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Re: Can lasers be made to curve without a prism?
« Reply #4 on: 22/02/2012 11:29:25 »
It's defined as 'space' bending due to 'gravity', so the laser would still shine 'straight', although to you curve.
 

Offline JP

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Re: Can lasers be made to curve without a prism?
« Reply #5 on: 22/02/2012 13:03:41 »
It basically all comes down to the fact that light takes the shortest* path between two points.  If you have curved space-time, the shortest path is no longer a straight line, but a curved path (much like the shortest path along the earth's surface between two points is a curve).  If the light is traveling through some medium other than vacuum, that material slows the light down according to its index of refraction (higher index = slower).  If light travels through such a medium, it changes direction to minimize its travel time, which is why it bends.

There is a branch of modern optics called transformation optics which uses the mathematics of general relativity to design material structures that bend light in some desired way.  (The well-known optical "cloaks" are an example of this.)  This field works because light takes the shortest path in both the GR case and the case of a medium with a varying index of refraction.

*: Actually, light takes an extremal path, which is either longest or shortest. 
 

Offline SeanB

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Re: Can lasers be made to curve without a prism?
« Reply #6 on: 23/02/2012 19:37:07 »
Many years ago there was research done on using hot air as a lens, with differential temperature being used to create a lens that was just hot air.
 

MeinKraftLover13370

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« Reply #7 on: 12/10/2015 02:14:54 »
Yor a fagit
 

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