Do you have thick or thin hair? Let’s find out using a laser to measure the width of your hair and a little knowledge about diffraction properties of light. (Since were using lasers, make sure you’re not pointing a laser at anyone, any animal, or at a reflective surface.)

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7 Responses to “Measure your Hair Width with a Laser”

  1. Colleen LaGrange says:

    We liked this experiment, Dad’s beard was the thickest. Mom’s hair was the thinnest. When we watched you measure the diffraction pattern it looked like your lines were 8mm apart not 8cm. That would make your hair 162.5micrometres not 16. Normal human hair is between 17 and 180 micrometres.

  2. If you put too much current through a laser diode, the number of photons bouncing around inside exceed the limits and effectively blow one or both of the end facets off, and ka-boom… end of laser. Here’s an article about the differences between red and green lasers.

  3. Mehak Chawla says:

    Why do green lasers burn out if you keep them on for to long?

  4. Let’s see if I can help. What were the measurements between the dark spaces that you measured? I can show you how to put it into the equation. Just make sure you’re really 1 meter from the wall, and also let me know the wavelength of your laser.

    Note: I really had a lot of trouble making a video because the camera didn’t pick up the ruler since the laser was so bright, and the laser diffraction pattern was hard to show on video so I used a still image to piece everything together so it would make sense. But it really does work when you follow the steps! 🙂

  5. Jennifer Harrison says:

    We could not get the experiment to work. I could have missed something or did something wrong, but our hairs, (we tried two to make sure) were the exact same width as your results. Also, I found that the numbers in the instructions did not match the equation that you gave later on. We may be doing it all wrong but could not get it to work.

  6. Daniel Ohanessian says:



  7. Christophe Landa says:

    That looks so cool ! ! ! Plus another awesome thing is you need so few materials!!!!!!!!!!!!!!!!!!!!!!! 🙂