405 nm laser fun

May 26, 2011 at 5:39 pm | | nerd, science and the public, science@home

I bought a 10 mW (30 mW, actually, according to our lab’s power meter) 405 nm laser from Amazon. No this pointer isn’t for presentations, for reasons I have already stated. This pointer is for fun.

For instance, I’ve enjoyed shooting the beam through tonic water and seeing the fluorescence from quinine. Here’s some total internal reflection:

Any other ideas for cool “experiments”?

(Note, please be careful with this or any laser pointer. Although the purple light emanating from this pointer doesn’t look bright, it can damage your eye or skin. Even if your eyes aren’t sensitive to 405 nm, that doesn’t mean they can’t be damaged by 405 nm. This pointer is dangerous to be viewed even in diffuse reflections.)

(P.S. The sorta shitty photo credited to E.Y.L.)

UPDATE: It turns out that urine is also fluorescent:

Especially after taking a multivitamin.


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  1. Perfect timing! I have one of these and I’m going to do some high school outreach tomorrow… definitely going to go pick up some tonic water on my way there!

    Comment by LMK — May 26, 2011 #

  2. Try it out with olive oil or ethylene glycol, very cool.

    Comment by ref — May 27, 2011 #

  3. Inbox stuffed with un-filed papers? Check
    More caffeine sources than pens? Check
    iTunes? Check
    Random baseball and pictures of the Death Star? …Check
    Ordered chaos on desktop? Check

    Yup, pretty standard lab desk :)

    ps Very cool picture of the “laser beam”
    pps What are they burning on your coffee mug over there? It looks like tires.

    Comment by azmanam — May 27, 2011 #

  4. Get a clear 2-liter soda bottle, and cut a small hole, about the diameter of a pencil, in it a few inches up from the bottom. Fill the bottle with water and cap tightly. The water should not be leaking out. Aim the laser pointer so that the beam is going through the bottle and coming out the hole. Loosen the cap, and watch the laser beam bounce off the air/water interface as the stream arcs downward. It’s a pretty good demonstration of fiber optics.

    You can also pick up some cheap mirrors, and see how many times you can bounce the pointer around the room. Do it with a fog machine or in a dusty room for extra coolness.

    Credit: the NASA teacher’s website, many years ago when I got my first laser pointer.

    Comment by Margie — May 27, 2011 #

  5. yeah, tires. a dumb joke. a tire is, by some stretches of the definition, one single molecule. because the polymer chains are cross-linked. hilarious, right?

    Comment by sam — May 27, 2011 #

  6. and the “death star” is data, dude! not the baseball. that’s my labmate’s data.

    Comment by sam — May 27, 2011 #

  7. Yeah I figured you didnt have a dozen print outs of the death star… :) What’s the data?

    Comment by Azmanam — May 29, 2011 #

  8. Since you’re already playing around with total internal reflection you could try to replicate the bending of water with radiation pressure as described in: http://focus.aps.org/story/v27/st18 which references http://link.aps.org/doi/10.1103/PhysRevLett.106.183904

    Comment by superkuh — May 29, 2011 #

  9. Azmanam, the data is FRAP.

    Comment by sam — May 31, 2011 #

  10. that’s really cool, superkuh. and i like the idea, Margie!

    Comment by sam — May 31, 2011 #

  11. EXCUSE ME, that photo is AWESOME, and without it you would have no blog post.

    Comment by EYL — June 23, 2011 #

  12. OK, OK. Shitty lens and detector. Superior framing and artistry.

    Comment by sam — June 28, 2011 #

  13. Tequila is also fluorescent to 405nm, the material disposal question comes after you’ve done the experiment… Tested! :)

    Comment by paco — November 5, 2011 #

  14. And if you get a lens, you can burst blue balloons within seconds of good focusing, tested as well

    Comment by paco — November 5, 2011 #

  15. yeah, several alcohols are fluorescence with blue or purple light:

    Comment by sam — November 6, 2011 #

  16. lol,dont forget that if you want to find whats florescent go for lower wavelength. have you tried it with anything phosphorescent or liquids that change the color?

    Comment by Long — December 1, 2011 #

  17. […] is one of the coolest things I’ve seen all year! I have a habit of shining my 405 nm laser pointer at fun things. But I was really surprised when I donned my safety goggles and the beam hit […]

    Pingback by Everyday Scientist » laser pointer and a fluorescent lanyard — January 8, 2013 #

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