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Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
anyone notices scattered laser light looks grainy? does this only happen to lights with a specific wavelength? cuz i can sort of see the same thing on some dim red LEDs
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
It happens with all light sources but it is only visible when the there is a narrow range of wavelengths. It is the same with sound, it is easy to hear the interference if you have a single pure tone. When you have many different wavelengths the speckles will appear at different places and the average will be smooth. When you move your head you change the phase and the speckles move.
Registered Member #2261
Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581
I heard once that the size of the individual speckles is equal to the resolving power of the optic observing the laser light, so presumably when you directly observe it they are at the resolving limit of your eyes. From my own observations that doesn't seem unreasonable.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Bjørn wrote ...
It happens with all light sources but it is only visible when the there is a narrow range of wavelengths. It is the same with sound, it is easy to hear the interference if you have a single pure tone. When you have many different wavelengths the speckles will appear at different places and the average will be smooth. When you move your head you change the phase and the speckles move.
The 'powdery light' of magnesium flares first described by TE Lawrence and others in the First World War is also spectrally defined - by the magnesium-gas line λ = 518 nm and the MgO-gas line λ = 500 nm
Registered Member #621
Joined: Sun Apr 01 2007, 12:37AM
Location:
Posts: 119
One thing i noticed is that the speckles stop moving if you stop your eyes, but if you move your perspective (your head) it looks as if they are "flowing". It definitely adds a neat aura to laser beams!!! i always loved that!
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why does laser light look grainy?
