Laser "microscope"

It doesn't matter if the laser is single ore multimode ossumguywill. Mine is symmetrical multimode and it works fine (as shown in the video )

I would recommend at least a 150mw green laser if you are doing this in a classroom, because the bigger the projection, the bigger the bacteria. Plus students don't like to get out of their seats. This one will be perfect.

You don't need to focus anything, the water droplet does the focusing for you. Just shine the beam into it. You want to use sticky tack (the blue stuff people use to hold up posters, get it at an office store) to hold the laser. It's what i did and it allows for nice fine adjustments. You'll want to get the beam centered in the droplet which isn't too hard. Here's a picture I did on MSPAINT that shows what to do.

The replicatability depends on the water. Pond water, freshwater fishtank water, anything that may be dirty.

Don't do this in the wind, because the water will start spinning and all you'll see is pretty much a blur. Close the windows and doors, and do it away from the A/C or heating vents.

Students don't mind getting out of their seats in my experience... being a student...

And good to know that multimode is OK.

Sam F said:

Hi everyone,

I'm here after seeing all of the hullaballoo over these really cool laser microscope videos.

I am a high school biology teacher, and I would really like to perform this experiment in my classroom. I think it would be an incredible introduction to the world of single-cell organisms. (And I bet the physics teacher would be just as interested in the optics side of it).

Before I spend a bucketload on a super-fancy laser, however, I've got some questions:

• I understand that you need a fairly high-powered laser, at least 50mW. Is that right?
• Are there any other technical specifications for the laser? I'm a laser newbie. Someone at work mentioned getting "single mode" lasers. Is this a requirement? Is the green color important?
• About how much should I expect to spend for such a laser? Do you have good recommendations for online stores?
• How replicatable is this experiment?
• How easy is it to focus the beam on the water drop?

Sorry if that's a lot of questions -- I'm just excited to get this in front of my kids. Any help you could provide would be great!

Thanks,
Sam

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High powered laser not required . Any legal (5 mW) laser pointer will do. I used a 15 mW red pointer for mine. See my post earlier in this thread.

You should not need to spend more than $25-50 dollars on a weak laser pointer (< 20mw). It might help to be able to focus the beam, though this isn't necessary.

Very easy to duplicate. The most difficult and important part is locating the pond water, with live creatures within. I live in Madison, WI and there are numerous lakes and ponds here. Nonetheless I had to collect water from three different locations before I found some water with lots of live critters. There were also some debris in the water. I kept the water in a small jar, and I made the video within an hour or two after collecting water. I'm not certain how long any organisms in the water will survive, though I doubt it's more than 48 hours.

Focusing the laser beam onto the water drop was difficult and took a lot of trial and error. I used a focusable laser pointer, and I focused the beam to a tiny speak where it hit the water droplet. It was difficult to keep the water droplets suspended from the dropper. Eventually I was able to project a small patch of laser light about a yard from the droplet onto the wall.

Here's a picture of my shoestring setup:


Here's a sample video from my above setup. You can see some larger critters and some small ones that appear as little discs:


Here's the best video I could find demonstrating how to do this on a tabletop. A 5 mW green laser pointer was used.


This really is a fun little experiment. Good luck finding some brackish water.

I still recommend at least a 100mW green. The entire wall lit up with the bacteria world is just spectacular. Plus the bigger the image, the greater the magnification.

Thanks for all your replies! I'm still trying to find a loaner laser from someone to test it before I buy a laser myself, but this seems like it will be really fun.

WRM said:

Here is the experiment done by Arbor Scientific. The narrator unfortunately misidentifies the wavelength of the laser; but the experiment works perfectly. The water acts as a small lens and assists in magnification. Bill

YouTube - Green Laser Microscope

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this moron calls his green laser a "650nm" :yabbmad::scowl:

SPammer!!!!!

Would an unfocused 300mW 650nm laser work for this?

Did this a few weeks ago with my watt laser. Pretty fun.

-Trevor

phoenix77 said:

We'd all have a lot more money than we do now. lol...................

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Great information! I’ve been looking for something like this for a while now. Thanks!