Experiment 10: Measuring a Human Hair

OBJECTIVE:
 The purpose of this experiment is to measure the thickness of a single strand of hair using two methods of measurement; one through the use of a laser, and the other through a micrometer.

FORMULAS AND DERIVATIONS:

PROCEDURE:

Hole through the index card with the strand of hair

Laser beamed through the hole across and projected onto the screen. (2 meter away).

Beam of light through index card. (front view)

Image of the laser pattern on screen. Bright fringes of the beam were marked indicating maximum values of the light wave.

Measurement of hair strand through a micrometer.

DATA AND ANALYSIS:

Measurement of the distance of the average distance between  bright fringes.  Three trials were done to  find the  average value. Circled point represents the center.

CALCULATIONS:

Laser Measurement
Length (m)	λ (nm)	YBright (m)	D (µm)
2.000 ± 0.005	650 ± 6.5	0.0189 ±0.002	69.7 ± 8.2

Micrometer Measurement

Thickness of hair (µm)

70 ± 5

CONCLUSION:

Based on the experiment data it can be verified that the thickness of the hair strand can be measured by the use of laser. The theory behind the experiment is that if a laser is beamed through an open slit then the distance of the tiny slit can be measured by knowing the wavelength of the monochromatic light, length of the screen from the light source, and the distance between the light fringes. These values help find the thickness of the hair or in other words, the distance of the slit. The thickness of the hair was also measured by using a more appropriate use of measurement, a micrometer. The micrometer would provide more accurate data, since its sole purpose is to make only measurements. There are too many variables that could skew the data when using the laser beam. There needed to be more precise measurements when measuring using a laser, since there are more variables that need to be considered. However, although there are many differences in both ways of measuring, the thickness of the hair between the two measurements came out to be approximately the same. The advantages to the laser measurments  

Laser Measurement

Length (m)

λ (nm)

Y_Bright (m)

D (µm)

2.000 ± 0.005

650 ± 6.5

0.0189 ±0.002

69.7 ± 8.2

Micrometer Measurement

Thickness of hair (µm)

70 ± 5

Laser Measurement

Length (m)

λ (nm)

Y_Bright (m)

D (µm)

2.000 ± 0.005

650 ± 6.5

0.0189 ±0.002

69.7 ± 8.2

Micrometer Measurement

Thickness of hair (µm)

70 ± 5