Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Are these pictures real?

  1. Oct 23, 2005 #1
    http://www.megalaser.com/gallery.htm

    they sell class IIIB lasers are these pictures genuine?
    can class IIIB lasers really show a beam without some medium like smoke?
     
  2. jcsd
  3. Oct 23, 2005 #2

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    One of the pictures claims to show the beam without fog. I am holding a class III laser in my hand right now (between keystrokes!) and I see no beam - just a bright spot on the wall! If there is, in fact, no fog then they have substituted something else like smoke or talcum powder dispersed in air.
     
  4. Oct 23, 2005 #3
    Bottom of the page. "*Please bear in mind that the camera exposes the beam in a different way than the naked eye."
     
  5. Oct 23, 2005 #4
    You can't see the beam without something in the air to reflect light.
     
  6. Oct 23, 2005 #5

    Claude Bile

    User Avatar
    Science Advisor

    The pictures look to have been photoshopped. They are certainly not real depictions of lasers in action.

    Claude.
     
  7. Oct 23, 2005 #6

    Pengwuino

    User Avatar
    Gold Member

    Yah the camera might have amplified it. Most cameras these days can adapt to low-light situations and one consequence might be that it makes a very very very very dim image (such as a laser going through the air) show up when a human would be unable to perceive it.
     
  8. Oct 23, 2005 #7

    Mk

    User Avatar

    omg those pictures were funny!

    "Its quite simply the most powerful laser in the world"'

    I'm still wondering how two AAA batteries supplies 15 Megawatts?

    Too bad some people would buy them.
     
  9. Oct 23, 2005 #8

    Pengwuino

    User Avatar
    Gold Member

    Well i assume they mean milliwatts since normal handheld lasers are in the milliwatt range
     
  10. Oct 24, 2005 #9

    Mk

    User Avatar

    Yes, of course. But the site clearly capitalizes the "m" making it MW Megawatts. The site is a fraud anyway, if a laser manufacturer made the site, it would have been mW.
     
  11. Oct 24, 2005 #10

    Pengwuino

    User Avatar
    Gold Member

    I don't see any capitalized mw
     
  12. Oct 24, 2005 #11
    I have a green laser pointer and its beam is very visible against a dark background. As I understand it, the reason we're able to see the green beam and not the beams of the more common red laser pointers is due to the fact that our eyes are much more sensitive to green light. Amateur astronomers use the green pointers for locating objects in the night sky because they're so visible. The photos posted here exaggerate the effect, but it is real.
     
  13. Oct 24, 2005 #12

    Claude Bile

    User Avatar
    Science Advisor

    20 Watt Copper vapour lasers produce a noticable green glow (within the cavity where the power densities are high), but it is quite faint.

    When the site says MW, they may be referring to the irradiance, (which actually has units W/m^2). In any case, the poor presentation of the manufacturers specifications means that many of the claims are probably exaggerated.

    In any case, the pictures are most certainly not real, and this in itself puts the credibility of the site very close to zero.

    Claude.
     
  14. Oct 24, 2005 #13
    I suspect that the pictures could be real, but taken with a lengthy exposure (perhaps several seconds).

    According to Wikipedia, high intensity lasers can be visible in clean air by Raman scattering or Rayleigh scattering.

    WiseGeek.com also suggests that green-beam lasers are visible in clean air.
     
  15. Oct 24, 2005 #14
    Looks like a manipulation of exposure time, look at the 3rd or so picture.
     
  16. Oct 25, 2005 #15

    Claude Bile

    User Avatar
    Science Advisor

    I considered that they may have used a long exposure time, however it is very difficult to hold a laser steady over a second or so, usually you get a star wars-esque lightsabre effect, which is why I suspect the photos have been digitally altered.

    I should also emphasise that the picture depicted in the wikipedia entry shows a clearly visible beam, however the beam is within the cavity where the energy density is typically much greater than the ouput beam (Also, I suspect the laser has substantially more power than the laser pointers if my previous experience with military research is anything to go by).

    Typically a beam has to be in the realm of Watts to be visible in the air, and even then it is faint.

    Claude.
     
  17. Nov 1, 2005 #16
    Not that I doubt you :wink:, but would you have any supporting references?
     
  18. Nov 1, 2005 #17

    brewnog

    User Avatar
    Science Advisor
    Gold Member

    Vaguely related popular culture fact:

    In the James Bond movie 'Goldfinger', the laser beam (in the scene where Mr Bond is not expected to talk, but to die) was drawn onto the film with a marker pen, or some such.

    The sparks flying off the steel bench that Sean Connery was strapped down to were created by a chap with an oxy-acetylene torch beneath the bench, working up to a chalk mark just beneath Mr Connery's crotch. The beads of sweat on the actor's face were real.

    /OT
     
  19. Nov 1, 2005 #18

    Claude Bile

    User Avatar
    Science Advisor

    Not off-hand, this is from personal experience in working with Copper Vapour lasers. I guess one could calculate what the scattered intensity would be, but that's not an exercise I'm willing to undertake right now :wink: .

    Claude.
     
    Last edited: Nov 1, 2005
  20. Nov 2, 2005 #19
    my friend bought an 80mw laser off www.wickedlasers.com and he says the beam is visible and the laser is very bright.
     
  21. Nov 2, 2005 #20

    Claude Bile

    User Avatar
    Science Advisor

    80 mW? I hope he wears eye protection when he uses it, cause that can do some serious damage.

    Claude.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Are these pictures real?
  1. Is this real? (Replies: 1)

  2. Picture Question (Replies: 12)

  3. Picture of a real atom? (Replies: 13)

  4. Solid Helium Pictures (Replies: 6)

Loading...