Measuring Human Hair

Introduction
           The purpose of this experiment is to measure human hair using 2 methods. The first one is by using a diffraction from laser and then figure out the distance from it. The other method is by measuring it directly using a micrometer. The accuracy will then be determined by calculating percent difference from the two methods which will give us the uncertainty.

Experimental
          The measurement of width of hair using the laser is set-up as follow:

Hair attached to the hole in the note card

Setup of the experiment using the laser

The interference in the laser observed

The data obtained by the laser experiment is as follow:

Wavelength (nm)	632.8
Distance to the board, L (cm)	180 ± 0.5
Distance of fringes, y (cm)	2.05 ± 0.02

Once the data is taken, the measurement with micrometer is conducted as follow:

Lab partners measuring using the micrometer

The reading of the micrometer

Once the data is taken and calculated, a table for compilation of data is made:

Width of hair using laser (µm)	55.56
Width of hair using micrometer (µm)	70.0
Percent difference	26.0%

Conclusion
             Based on this experiment, the width of human hair is about 62.78µm. The theoretical width of human hair cannot be determined in this case so percent error is impossible to calculate. The width of human hair is impossible to be determined theoretically because the width of hair of a person differs from one another so the theoretical values is actually a range that we cannot use to calculate percent error. The only thing that can be analyzed using the range is that both measurement is inside the range of the human hair width.
           The value that is more relevant to look at is the percent difference of the value of the two methods. By using these two methods, laser and micrometer, we determine it to be 26% difference in the value. Some error that could contributes to this is the fact that the micrometer itself is not a really accurate tool as hair can be as thin as 17 µm which makes it less accurate the smaller it gets. From the laser experiment, it is quite difficult to have the laser perfectly aligned with the board. There will be some angle created from the laser, slit and the board which makes the calculation a little bit off.