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why do lasers look grainy?
What I mean is if you look at a laser dot shining onto something, (not directly of course or you fry your retina)...or a laser line, you can see a grainy glow around it. if you look closely or long enough, you can see the grains of the glow sort of animate slowly, swimming around.
maybe the animation can be explained by not having a perfectly still head?
maybe the different points of light that produce the grainyness are reflecting off the imperfections of the surface?
Or is it because of intensity/wavelength that has this effect on the human eye and scrambling visual signals?
The "speckle" effect is caused by the laser light interfering on the surface of your retina after it scatters off the screen(or whatever). The effect is similar to the double slit experiment you may learn in school, which shows that light can cancel out (i.e. two beams added together can add to nothing). You don't see the effect with normal light because it is not coherent or in phase (not ordered).
Interestingly the "grains" are not actually on the screen (the screen is illuminated evenly) but in your eye(due to the difference in path length of the different light sources from the screen to your eye), everyone gets a slightly different pattern depending on their position. This is why it looks strange when you move.
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