Did you know that you can use a laser to see tiny paramecia in pond water? We’re going to build a simple laser microscope that will shine through a single drop of water and project shadows on a wall or ceiling for us to study.


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Here’s how it works: by shining a laser though a drop of water, we can see the shadows of objects inside the water. It’s like playing shadow puppets, only we’re using a highly concentrated laser beam instead of a flashlight.


If you’re wondering how a narrow laser beam spreads out to cover a wall, it has to do with the shape of the water droplet. Water has surface tension, which makes the water want to curl into a ball shape. But because water’s heavy, the ball stretches a little. This makes the water a tear-drop shape, which makes it act like a convex lens, which magnifies the light and spreads it out:


Here’s how to make your own laser microscope:


Materials:


  • red or green laser (watch video for laser tips)
  • large paperclip
  • rubber band
  • stack of books
  • white wall
  • pond water sample (or make your own from a cup of water with dead grass that’s been sitting for a week on the windowsill)


Download Student Worksheet & Exercises


Exercises


  1. Does this work with other clear liquids?
  2.   What kind of lens occurs if you change the amount of surface tension by using soapy water instead?
  3.   Does the temperature of the water matter? What about a piece of ice?
  4.  Does this work with a flashlight instead of a laser?
  5.  Do lasers hurt your eyes? How?

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Comments

8 Responses to “Laser Microscope”

  1. The goal is to notice the fine detail in the whiskers.

  2. What specifically are we looking for on Abraham Lincolns neck?

  3. If the material is transparent enough, yes the laser light will be able to pass through. Some materials will block the laser light, others will allow it to pass through.

  4. so does that mean no because if the laser bright it can still pass trough

  5. You need the light to pass through the medium in order to pick up the “shadows” that appear on the wall. Does that help?

  6. can the laser microscope see solids not just liquids

  7. I never realized it before, but I actually don’t just have that experiment by itself in the e-Science program! I will post it in Unit 9, but in the meantime, it’s part-way through the teleclass in Unit 9 on light and lasers (the first video near the top, Unit 9 Module 1).

  8. imuacares says:

    Hi
    When we watched your free webinar marine biology class you did an experiment with a laser microscope of pond water, well we finally got our lasers and I’m trying to find that experiment to know who to make the paper clip.
    Thanks,
    Ciera