![]() ![]() I hoped this set up would allow for customizable levels of darkness so as to improve my ability to see the precise edges of the diffraction pattern’s bands, and I eventually added a hole in the lid which corresponded to an identical hole in the box frame and cut a series of dowels varying in size so that the box’s lid could be suspended at differing heights depending on how illuminated I wanted the inside of the box to be. I initially used a piece of MDF fit to the exact dimensions of the box top attached with 3/4” strap hinges. I measured the bands using digital calipers set to metric units to the thousandth decimal place, a method that I thought would yield highly precise results, but the patterns presented with an almost fish-eye quality that I attribute to the shorter distance and which I believe contributed to my less than ideal results.Īnother obstacle in my attempts at precise data taking was in the design of the experimental enclosure’s lid. This downscaling of the set-up created diffraction patterns that were quite a bit smaller than I would’ve liked, meaning that the accuracy with which I measured the space between the bands was unacceptable for taking accurate measurements with the digital calipers. I set it up this way based on the set up of a similar experiment that I found online which I scaled down to fit the fiberboard box that I built to house the experiment. The distances I used were 10 and 35 centimeters respectively, meaning that the total distance between laser and MDF was 45 cm. First, the distance between my hair-holding frame and the laser itself as well as the distance between the hair-holding frame and the MDF board on which the diffraction pattern was projected is too small. Unfortunately I think there were more failures than successes with this initial experimental setup, enough that I felt the need to readdress the experimental design and retake the data. The numbers seemed random and the only clear pattern I could discern was in one student’s results his average head hair thickness was significantly higher than other subjects perhaps due to his south Asian background. To make things even simpler, the numerator in my equation can simply be the laser’s wavelength because I am only measuring to the pattern’s first minimum, meaning that m is 1.Īt the end of initial data taking, I was not impressed with my results. Theta in this equation represents the angle of diffraction, and because this angle is very small, I can use the small angle approximation formula, which is the distance measured to the first minimum (or band) from the pattern’s center divided by the distance from the hair to the projection surface. Using this formula in each measurement trial, I will plug in the distance, which has been standardized by the fixing of the laser to the inside of the box, and the known wavelength of the laser, either 532 nm or 473 nm, to find the diameter of the hair. The diffraction pattern will be measured with digital calipers and this measurement will be taken from the center of the pattern’s brightest point to the edge of the pattern’s first ‘dark patch’ in millimeters to the nearest sig fig. This plate was positioned exactly perpendicular to the laser to ensure that the measurement of the diffraction pattern was not skewed by the angle from which the laser emitted. It will pass around the item to be measured, which will be fixed level to the laser and 1” away from its tip by a small frame made of 5mm thick sheet metal held steady between two halves of a 2 x 4, and will project a diffraction pattern on a piece of 1/4” thick MDF plate at the other end of the box. The laser will be fixed to a wooden mount and shine from the inside of one end of an originally 1’ x 2’ x 6” rectangular prism made of 3/4” thick medium density fiberboard, wood glue, and pocket-holed screws. Each student will provide three hairs and the diameters of each will be calculated and averaged together, using both colors of laser light in an effort to see which of the two provide more precise measurements. My project consists of the diffraction of laser light of 2 known wavelengths around the hair follicles of several Vassar students. ![]()
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