Measure a human hair by using the principle of single slit diffraction producing predictable minima.
Materials:
A human hair, a hole punched card, and a laser pointer.
Procedures:
1. Mount a strand of hair to an index card with a hole in it
2. Shine a laser passing through the hair
4. Measure the parameter y and L, with the known parameter lamda of laser = 632.8 nm = 632.8*10^-9 m
5. Find d - the thickness of hair
Data obtained:
The data obtained by the laser experiment is as follow:
Wavelength (nm)
| 633 |
Distance to the board, L (cm)
|
100 ± 0.5
|
Distance of fringes, y (cm)
|
1.05 ± 0.02
|
d = 632.8*10^-9/1*10^-2 = 6.33*10^-5 m = 0.0633 mm
Conclusion:
The average hair thickness of online sources(expected value): 0.09 mm - 0.25 mm
Out result does not fall within this range, but it is in the same order of magnitude.
Error(lower): abs(0.0633-0.09)/0.09 = 30 %
Error(upper): abs(0.0633-0.25)/0.25 = 75 %
* The use of micrometer to measure the thickness of human hair is not an accurate method, as least compared with out main experiment, because of the limitation on the magnification of the equipment compared with the actual order of the thickness.
Out result does not fall within this range, but it is in the same order of magnitude.
Error(lower): abs(0.0633-0.09)/0.09 = 30 %
Error(upper): abs(0.0633-0.25)/0.25 = 75 %
* The use of micrometer to measure the thickness of human hair is not an accurate method, as least compared with out main experiment, because of the limitation on the magnification of the equipment compared with the actual order of the thickness.
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