Experiment 10: Measuring a Human Hair

Purpose:  Use a laser pointer  to give an approximation of how thick a human hair is and then use a micrometer to verify our calculations

Materials:

• 3X5 card with hole in it
• single strand of hair
• ruler
• laser pointer
• micrometer

Set Up:

A red laser with wavelength of 660 nm was aimed through the notecard with a hole in it at a white board.

 The hair acts as a diffraction grating, dividing the laser point into multiple minima and maxima.

 Data/ Calculations:

This is the calculation of the width of the hair since the hair acts as a diffraction grating.

y in the equation is the distance between the fist order maxima and the center dot

L is the distance from the notecard to the whiteboard.

and d is the diffraction grating/ thickness of the hair.

Then we tested our results by measuring the hair directly with a micrometer. This reading gave us
50 ± 20 μm

Conclusion: This experiment gave us a measurement that fell within uncertainty of our calculated value for the thickness of the human hair even though our percent error was found to be 65%.