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Author Topic: yet ANOTHER question about Light !!!  (Read 3684 times)

Offline neilep

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yet ANOTHER question about Light !!!
« on: 23/11/2007 23:22:28 »
Oh dear !!

If a laser is sending a light beam/ray in one direction....how can I see the light beam from the side ?

Isn't it traveling in a straight line ?.....does light emit light in all directions ?




Quality drawing !!

« Last Edit: 23/11/2007 23:24:01 by neilep »


 

Offline Karen W.

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yet ANOTHER question about Light !!!
« Reply #1 on: 23/11/2007 23:30:27 »
Yes, quality Indeed !!
 

Offline daveshorts

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yet ANOTHER question about Light !!!
« Reply #2 on: 24/11/2007 00:07:09 »
If it is travelling through a vacuum you can't.

However this looks rubbish in photos / films so they tend to spray some smoke in the way which scatters the beam sideways occasionally and into your eyes. With quite strong beams dust in the air can also sometimes make them visible
 

another_someone

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yet ANOTHER question about Light !!!
« Reply #3 on: 24/11/2007 01:01:06 »
Oh dear !!

If a laser is sending a light beam/ray in one direction....how can I see the light beam from the side ?

Isn't it traveling in a straight line ?.....does light emit light in all directions ?




Quality drawing !!



Does this not come under the same issues as your earlier question about crossed beams of light of different colour.

http://www.thenakedscientists.com/forum/index.php?topic=10938.0
 

Offline neilep

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yet ANOTHER question about Light !!!
« Reply #4 on: 24/11/2007 02:07:01 »
THANK EWE DAVE, and THANK EWE KAREN for the appraisal of my work !!

....GEORGE...the last time I asked about Light was whether the two different coloured beams of light would affect the colour of each other when they intersect.....nothing to do about my question above regarding viewing it from the side.

Perhaps it does come under the same issues though......maybe I should start yet another light thread and ask about it !! ;)

 

lyner

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yet ANOTHER question about Light !!!
« Reply #5 on: 25/11/2007 17:14:12 »
If your beam is passing through some dust in the air, say, then some light is scattered from the main beam.
Observing the light scattered from the beam from the side and modulating the beam into pulses,  you would  see  the pulses (with the light scattered  from two places on the beam) at different times; the second one would be delayed. You wouldn't need particularly nifty equipment by modern standards  to see this - with a 100m baseline, you would  be looking for a whole 0.3 microseconds difference in the time of arrival of the two pulses to where you are standing; easy peasy with a Cheapo oscilloscope and  Maplin quality sensing equipment.
But the light beam is still going in a straight line.
 

Offline syhprum

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yet ANOTHER question about Light !!!
« Reply #6 on: 25/11/2007 22:40:17 »
Although the divergence of a laser beam is quite small it is not zero.
The laser ranging beam that is used to check the Earth/Moon distance has am effective width of 4 Km when it reaches the Moon 
 

lyner

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yet ANOTHER question about Light !!!
« Reply #7 on: 26/11/2007 09:34:19 »
Quote
Although the divergence of a laser beam is quite small it is not zero.
The laser ranging beam that is used to check the Earth/Moon distance has am effective width of 4 Km when it reaches the Moon 
I'm not quite sure what you are getting at, here. Yes, of course the beam will diverge - diffraction will always apply and the best you can do is to attempt to focus your beam at a distance. The light is still going 'straight' and not following a curved path or spreading out so that it can get into your eye.
The only way you can see the beam from the side is when light is scattered from it by hitting something.
 

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yet ANOTHER question about Light !!!
« Reply #7 on: 26/11/2007 09:34:19 »

 

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