Measuring a Human Hair

Introduction:

The thickness of a human hair is about 50-150 micrometers.  In this experiment we will use interference patterns of light caused by a single human hair.  The hair acts as separator in a Young's double slit experiment and the thickness of it can be calculated as the d parameter in the equation

where y is the distance between adjacent interference maximas, lambda is the wavelength of the laser we will use, L is the distance between the hair and the screen of the patterns.

Steps:

The apparatus is depicted below:

For ease of measurement, a meter stick serves as the distance L.

Interference patterns observed (Previously marked patterns are shown above the laser lighting).

The distanced between markings were averaged after using calipers.

A micrometer is used as a means to compare our experimental data.

The results are tabulated below

Questions/Conclusions:

Using interference patterns to measure the diameter of the human hair is only so reliable.  We obtained a percent error of 9.2%, and were satisfied with the results since the interference equation involves many parameters that lead to greater uncertainty.  The micrometer has a sole purpose in measuring objects in these scales and so it was taken as the control in this experiment.