In this case, it means I take my average measurement from my seven people (2.2 centimeters) and divide it by the wall distance (187 centimeters). We can get this by dividing the measurement from your light scatter by the distance between the hair and the wall. Is the angle at which the light scatter occurs. , the Greek letter lambda, is the wavelength of the laser, in this case, 650 nanometers or 0.000065 centimeter. Since I measured to the first dark gap, m is one. Is the minimum gap distance that is measured on the scatter. Make sure to measure the distance between the hair and the wall. Then, I put the numbers into the equation provided in the video: Average light scatter of the hairs of the seven people I sampled: 2.2 centimeters.Laser wavelength: 650 nanometers or 0.000065 centimeter.Distance between my hair and laser and the wall: 187 centimeters.I converted all of my numbers to centimeters. It will help to make sure that all of your numbers are in the same units. Now, you have all you need to figure out how thick your hair is. It’s usually best to have a buddy, one person to hold the laser pointer and hair, the other to measure the pattern. You want to measure the line from the center of the dot to the first major “dark” section. Usually this is listed on the laser pointer itself.Ĩ. A red laser pointer will be about 650 nanometers and one issuing a green light will be about 532 nanometers. Check the wavelength of light produced by your laser pointer. It’s best to measure this in centimeters.ħ. Measure the distance from your hair to the wall where you are shining your pointer. This means that by measuring the size of your light scatter, you can - with a little math - figure out the width of your hair.Ħ. The size of the pattern from this diffraction is related to the size of the object that caused the scatter. It will create a scatter pattern you can see on the wall. Light can act as a wave, and when it encounters the hair it splits into a regular pattern of lines. Diffraction is the bending that takes place when a wave of light encounters an object, such as a human hair or a slit in a piece of paper. The hair is causing the laser’s light to diffract. Shine a laser pointer toward a wall, making sure it hits the hair on the way. You will see the light scatter to the sides as you hit the hair with your laser pointer. Hold up the frame with your hair, and shine a laser pointer at the wall from just behind the hair, making sure it hits the hair along the way.ĥ. In a dark room, stand more than a meter (more than three feet) away from a blank wall. Tape the hair, as tight as you can, at the top and bottom of your frame, so that the hair runs through the middle of the inside cutout.Ĥ. In my case, each hair had to be at least 5 centimeters long to make sure I could tape it at both ends.ģ. Make sure it is long enough to tape at both ends of your inside rectangle. Take a human hair, maybe from your own head, or from a willing volunteer. My inside cutout was about one centimeter (0.39 inches) wide and four centimeters (1.5 inches) tall.Ģ. I cut a square of cardboard about 15 centimeters (roughly six inches) wide, and then cut a small rectangle inside it. Here, Chris Crockett holds one of my hairs. To find the width of a human hair, start by taping your hair into a small cardboard frame. Then I measured how they scattered the light from a laser pointer with the help of fellow writer Chris Crockett. Using a useful video with instructions from the Frostbite Theatre YouTube series at the Department of Energy’s Jefferson Lab in Newport News, Va., I decided to see if I could measure the hairs of some of the writers here at the Science News office. All you need is a dark room, a laser pointer, some cardboard, tape and a little bit of math. You can measure the width of a single hair. You can repeat the steps here and compare your results - or use this as inspiration to design your own experiment. This article is one of a series of Experiments meant to teach students about how science is done, from generating a hypothesis to designing an experiment to analyzing the results with statistics.
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