Pointing an 8MW against a window at an angle

Hello!

I've bought a little 8mw green laser from optronics, i'm wondering if pointing this at an angle to a window will reflect some of the light back to me and be dangerous.

Thank You!
Best Regards

Pointing an 8MW (MegaWatt) laser at anything is a bad idea. An 8mW (milliwatt) laser is a difference story lol. Specular reflection from an 8mW laser is not an issue.

To anwer your question, angle of incidence is equal to the angle of reflection...



http://lukewest.edublogs.org/2009/09/24/reflection/

IF it were truly a 8mw AND you were to hold it at the perfect angle a little of the beam might bounce back and if you stare at it you could cause some mild problems but it would be so unlikely that you could dismiss it.
However, I am interested to know where you got a 8mw 532nm laser from.
Is it a properly tested overpowered 5mw ? Usually the "5mw" ones are much more than just 8mw. more in the order of 15- 35mw I believe is more likely.
So if you are playing with a much higher power instrument then OF COURSE the dangers will be so much greater. What are you pointing through a window at ? If you are worried about the reflected beam then you are pointing it at something the same height as you are at and that means that it could be falling well within eye level of others on the other side of the window.(Unless you are in a multi-story building.)
More importantly is that if you aim it perfectly the bounce back beam could feed directly back into the laser and overpower it causing damage. Pfffft. It's gone.
But a low power laser wouldn't have much of an issue with reflection.

Geez Infinitus. Respond faster than me why don't ya ?
I'm feeling older all the time.

ShortyInCanada said:

Geez Infinitus. Respond faster than me why don't ya ?
I'm feeling older all the time.

Click to expand...

Sorry buddy, I type fast:san:

8mW is above what is safe, I'd recommend to treat it as the class 3b laser that it is. I think 5mW is pushing the limit, pushing it to 8mW is a bad idea. Of course there are safe situations, but don't think you're always safe because it's only 8mW, that would be very wrong.

Thank you all for your responses

I bought the greenie from jack at optotronics.com, so we can be reasonably sure it's outputting 8mW, instead of the 8 MW i told you

i was pretty sure it was reasonably safe but i wanted to be completely sure. and i'm also sure there is no one on the other side of the window because i like in a pretty tall building, and yes i'm always looking out for airplanes!

since this is a window, i believe it would reflect back less than 50% of the light, meaning it would still be under 5mW. i would of course blink.

Best Regards

Windows are 10%-20% reflective.

joeyss said:

Windows are 10%-20% reflective.

Click to expand...

I've never been able to measure higher than 10% personally.

One pane of perfectly clean and perfectly flat glass should reflect 8% light (without optical losses in the glass), in two very closely grouped dots. Each side of the window pane will reflect 4%. If it's a double pane window, it can reflect 16%, but there would be an optical loss in passing through the glass. Essentially, you have little to worry about. I've shone several-hundred milliwatt lasers at glass, simply being careful or where it might reflect (although I wouldn't do this if you are clumsy or inexperienced, and even then you always want to be wary of reflections off anything). You would not have to worry about this with an 8mw laser, but perhaps with a >500mw or class IV laser (this is where the risk would become quite significant, but you should exercise the caution you would have with a class IV laser, with any laser that is perhaps >50mw).

I am not disregarding laser safety, but I believe many over react in saying an 8mw laser is dangerous; it's not.

Thanks,

AAlasers

AAlasers said:

I am not disregarding laser safety, but I believe many over react in saying an 8mw laser is dangerous; it's not.

Thanks,

AAlasers

Click to expand...

We are not all experienced Laser Technician/Engineers/Gurus....
and to say we overreact when it comes to Laser Safety pointed
to a Laser Noob is just plain irresponsible.

It is always better to be TOO safe than not safe enough when
dealing with Lasers... even 8mW Lasers...


Jerry

Bluefan said:

8mW is above what is safe, I'd recommend to treat it as the class 3b laser that it is. I think 5mW is pushing the limit, pushing it to 8mW is a bad idea. Of course there are safe situations, but don't think you're always safe because it's only 8mW, that would be very wrong.

Click to expand...

meh, id just say anything below 20mW is not dangerous, unless you point it directly to your eye. Reflections from mirrors are a bit on the dangerous side okay, but nothing to wild.
And reflections from glass is not dangerous at all, when dealing with <20mW.

but well.....act as an adult when holding a laser.

borgqueenx said:

meh, id just say anything below 20mW is not dangerous, unless you point it directly to your eye. Reflections from mirrors are a bit on the dangerous side okay, but nothing to wild.
And reflections from glass is not dangerous at all.

but well.....act as an adult when holding a laser.

Click to expand...

Pray tell... did you pull these nuggets of wisdom out of your A$$....:thinking:

To post that is so irresponsible that you should be ClueByFoured
right here on LPF....:banned:

Seems like you have learned absolutely nothing about Laser
Safety even with all the Thread questions that you have asked
since joining the Forum...


Jerry

lasersbee said:

Pray tell... did you pull these nuggets of wisdom out of your A$$....:thinking:

To post that is so irresponsible that you should be ClueByFoured
right here on LPF....:banned:

Seems like you have learned absolutely nothing about Laser
Safety even with all the Thread questions that you have asked
since joining the Forum...


Jerry

Click to expand...

i have learned alot, but also experienced alot. shining at stuff usally increases divergence as well when it bounces back, plus how long you get the beam in your eye also counts ect ect ect, you know this yourself as well.
I said it is dangerous pointing it directly to eyes. but heck that is even dangerous with a 1mW pointer. who knows if the guy cant have sudden light changes?
but with <20mW its my opinion that it cant be a real dangerous laser.

please, be a bit nicer to me the next time, and ask why im saying that, instead of voting for a ban immediatly.

this "wisdom" is pulled by experience, not by only making calculations.

Oh and you marked "And reflections from glass is not dangerous at all." red.
i ofcource ment this with a <20mW pointer. NOT globally.
sorry about that, will edit the post.

If you can GUARANTEE that anyone will not make a mistake
and inadvertently shine a reflected 19mW (<20mW)laser beam
into their eye for less time than it could cause any eye damage
under any circumstances... then I could possibly agree with your
understanding of Laser safety practices.

If not... then I would err on the side that shows me a safer
way to handle Lasers Safely and especially to new members
that are looking for advice to keep their eyesight undamaged...

BTW... you are allowed to handle your lasers in any way you
want... They are your Eyes are not mine...:san:


Jerry

lasersbee said:

We are not all experienced Laser Technician/Engineers/Gurus....
and to say we overreact when it comes to Laser Safety pointed
to a Laser Noob is just plain irresponsible.

It is always better to be TOO safe than not safe enough when
dealing with Lasers... even 8mW Lasers...


Jerry

Click to expand...

Very true, but you seem to be ignoring the rest of what I said, in my last post. I was referring to dealing with reflections from windows, and other reflective objects. I never said to be a complete idiot with a laser, as you insinuate, or to completely disregard laser safety.
I am very well aware that not everyone who owns a laser is experienced in it's safety, and of course there is a certain level of respect to be had for lasers, but a laser of such a low power level, perhaps <20mw as borgqueenx suggests, is not anything you must worry extensively about.

That being said, it is probably more wise to suggest that one would assume all lasers to be highly dangerous, no matter the power level; that way they will develop good habits in dealing with lasers. Additionally, one might make the mistake of assuming a high powered laser as having a lower power then it does, which is a truly grave mistake in the guise of safety. Considering all do not have the experience and judgement regarding laser safety that you or I might have, I ought to agree with you and say all lasers are to be treated as dangerous devices - particularly directed to the inexperienced.

My apologies if I seemed a little irresponsible in my last post, I had no intention of causing hard feelings, or making the inexperienced regard laser safety to a lesser degree.

Thanks,

AAlasers

AAlasers said:

Very true, but you seem to be ignoring the rest of what I said, in my last post. I was referring to dealing with reflections from windows, and other reflective objects. I never said to be a complete idiot with a laser, as you insinuate, or to completely disregard laser safety.
I am very well aware that not everyone who owns a laser is experienced in it's safety, and of course there is a certain level of respect to be had for lasers, but a laser of such a low power level, perhaps <20mw as borgqueenx suggests, is not anything you must worry extensively about.

That being said, it is probably more wise to suggest that one would assume all lasers to be highly dangerous, no matter the power level; that way they will develop good habits in dealing with lasers. Additionally, one might make the mistake of assuming a high powered laser as having a lower power then it does, which is a truly grave mistake in the guise of safety. Considering all do not have the experience and judgement regarding laser safety that you or I might have, I ought to agree with you and say all lasers are to be treated as dangerous devices - particularly directed to the inexperienced.

My apologies if I seemed a little irresponsible in my last post, I had no intention of causing hard feelings, or making the inexperienced regard laser safety to a lesser degree.

Thanks,

AAlasers

Click to expand...

No apologies needed... No hurt feelings here...
Can't agree more....
I was leaning towards exactly that...:beer:

Jerry