Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Visibility: Laser coming towards you versus laser travelling away.

Marco Polo

New member
Joined
Nov 2, 2012
Messages
617
Points
0
I haven't seen any threads discussing this particular topic. I think it's a good one to look at, if only because it's interesting, but it could have practical implications. I'll leave it as an exercise to the reader to think of what situations and how :)

Earlier this year, during the summer, but also indoors with smoke in the air, a friend and I were pointing lasers in each other's general direction and I didn't expect the incoming beams to look as bright as they did. I'm accustomed to seeing the beams travelling away, because usually I'm the one pointing the lasers at things. (but not at people, that's dumb.) I don't usually have them coming back at me. Seeing it happen surprised me because the incoming beam is a lot brighter than the beam going away.

I grabbed a small mirror, lit up some incense, and took some pictures. Even the 5mW red looked bright when reflected back.

ETA: Be careful when pointing lasers at mirrors. You might want to wear safety glasses since the reflections are basically 100% power. The lasers in these photos are Class IIIb and they are more than bright enough. Even the little 5mW makes a visible reflection. I would leave any Class IV lasers in their storage cases - way too dangerous to use them around mirrors.

Lazerer LZCS 450nm 127mW


Skylasers 520nm 50mW


AtlasNova 635nm 5mW


ETA: Three lasers - Skylasers HL450 and HL520, Lazerer LZCS 532nm


Pretty cool! Forget lasering anyone and thinking you're being stealthy - the beam they see is a lot brighter than what you see, and it points right back to where you are. They look as bright with incense smoke as they did on a humid summer evening.
 
Last edited:

Atomicrox

Well-known member
Joined
Jun 22, 2011
Messages
2,432
Points
83
Indeed it does. You can even see beams that would otherwise be too weak to see!

The only problem is that many lasers have slpash/wings/whatever and it's very easy to get hit directly with the splash before you notice, since it's too weak to show up as a beam. I got hit by the wings of my 520nm laser, it's very annoying (glad it was low power). Now I take a lot more caution to identify all the splashes before doing this.
 

Grix

Well-known member
Joined
Dec 9, 2008
Messages
2,212
Points
63
This is because the light doesn't scatter uniformly, more light is scattered in generally the same direction as the original beam.
 

steve001

Well-known member
Joined
Jun 3, 2007
Messages
2,193
Points
83
I haven't seen any threads discussing this particular topic. I think it's a good one to look at, if only because it's interesting, but it could have practical implications. I'll leave it as an exercise to the reader to think of what situations and how :)

Earlier this year, during the summer, but also indoors with smoke in the air, a friend and I were pointing lasers in each other's general direction and I didn't expect the incoming beams to look as bright as they did. I'm accustomed to seeing the beams travelling away, because usually I'm the one pointing the lasers at things. (but not at people, that's dumb.) I don't usually have them coming back at me. Seeing it happen surprised me because the incoming beam is a lot brighter than the beam going away.

I grabbed a small mirror, lit up some incense, and took some pictures. Even the 5mW red looked bright when reflected back.

Lazerer LZCS 450nm


Skylasers 520nm


AtlasNova 635nm 5mW


Pretty interesting. Forget lasering anyone and thinking you're being stealthy - the beam they see is a lot brighter than what you see, and it points right back to where you are. They look as bright with incense smoke as they did on a humid summer evening.
You'll find this demonstration interesting.
Laser Pointer Experiment
And this one too.
laser contact to france

When the weather is nice get your friend and do something similar.
 

ImA4Wheelr

Member
Joined
Nov 28, 2013
Messages
122
Points
18
Are we witnessing the Doppler effect in those pictures? There seems to be a shift in color. Especially, in the first picture.
 

ultimatekaiser

Well-known member
Joined
Mar 10, 2013
Messages
2,830
Points
83
This is because the light doesn't scatter uniformly, more light is scattered in generally the same direction as the original beam.
This is the correct reason. Over twice the amount of light is scattered forward, rather than backward.
 

supermario680

New member
Joined
Sep 29, 2013
Messages
97
Points
0
exactly, when in front of the beam you will see light that is only scattered a few degrees, but when viewing from behind you will only see light that is reflected a FULL 180 degrees back to you. A much smaller portion.
 

olo manolo

New member
Joined
Jan 2, 2014
Messages
8
Points
0
Are we witnessing the Doppler effect in those pictures? There seems to be a shift in color. Especially, in the first picture.
Nope. Doppler effect refers to the change in frequency of a wave moving relative to the observer. Something would have to be moving towards/away from the mirror to have any sort of Doppler effect.
 




Top