As RaceProUK already said, you can not see a laser beam (or any light for that matter!!!) if it does not reflect on something...
Smoke, haze, watervapor, dust, etc are all things which can be used to make laser light visible. All those substances are... substances, and if they come in the path of the beam of light (again, any light, doesn't need to be 'laser') the light will reflect on there surfaces. Some of that reflection will be towards your eye, hence you will see the beam...
The more light that is being distributed, the more change it has as a whole to reflect on something. Hence why powerfull lasers (eg: green lasers are in general more powerfull than red lasers) are visible, even without additional stuff in the air... That is: without additional stuff in the air on first sight, because there is always something in the air (isn't that from a song
)....
A normal flashlight is also visible on misty nights, because even that faint light is reflected by the massive water vapor in the air.
If you shoot a laser thru a tube without any air or other particals, you wont see anything at all, ever because there is nothing to reflect the light of...
quote:
Originally posted by Nagamasa
Would viewing through a one-way mirror work?
yes, unless you close your eyes or you're trying to look thru it on the wrong side...
to be serious: if you point the laser beam at the mirror it will reflect and it will go in the opposite direction under the opposite angle. When you look at this beam on the other side of the mirror, you will only see a dot on the mirror.... Unless, again, if there is enough stuff floating around in the air to make the beam visible. If so, you will see a beam projecting on the mirror and reflecting away (and you will also see a smaller/dimmer beam shooting right thru the mirror
(depending on the hardness of reflection of the mirror and the power of the laser) but under a slightly bend angle)...
Do not experiment with lasers, unless you know absolutely what you're doing and know exactly all the physics and dangers involved!!! Even a split second in your eyes can/will make you permanently blind, not to mention possible severe burnwounds
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