Scientific Seen

News, Commentary, and Tutorials from a Scientific Perspective

Maybe you’ve made your own cheese, or installed a solar panel, or you’re filtering seawater for your aquarium. Anytime you have some kind of physical process in place, you’d probably like to monitor it so you know what’s going on and you know when you’re having a problem. With your own monitoring system, you can measure temperature, current, salinity, or just about anything else you need to track with digital panel meters. But you need to know the reading displayed is accurate. That’s why you calibrate your meter.

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Originally published in eHow, OCT 2011

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Nearly everything that uses electrical power has semiconductor circuits: your car, your coffeemaker, your computer. The performance of those circuits stems from the behavior of electrons within an ordered array of atoms, or a crystal lattice. Usually, the lattice is made from a base material of silicon atoms, with “dopants” added to increase or decrease the number of electrons in the material.

“N-type” semiconductor is made by introducing a dopant such as phosphorus, which brings extra electrons, whereas “p-type” has a dopant such as boron, which reduces the number of electrons compared to the base material. The interesting properties take place at the junction, where n- and p-type materials are brought into contact with one another. One of the things that happens is that the extra electrons from the n-type make their way to the p-side, and the missing electrons from the p-side, called “holes,” make their way to the n-side. The region in between is emptied of charge, hence the name “depletion region.”

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Originally published at eHow, SEP 2011

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Fire is hypnotic. Sit any group of campers around a nighttime fire, and you’ll notice their attention drawn by the constantly shifting interplay of form and color. Observing the sun offers that same fascination, enhanced by the knowledge that the flames of the sun support all life on Earth. The roiling, popping, swirling outer surface of the sun is best seen with one particular narrow part of the spectrum, the hydrogen alpha line, which is one particular wavelength of red light. The wavelength is 656.28 nanometers, or 656.28 billionths of a meter. The principles behind a filter that will isolate that wavelength are clear.

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Originally published at eHow, SEP 2011

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Every system that transmits information has some kind of speed limitation. The speed limitation is characterized by the bandwidth. One way of characterizing the bandwidth of a system is by observing its response to a pulse. As with any communications link, there are two ends: a sender and a receiver, and the measured speed will be due to characteristics at both ends. The best way to characterize such a system is by doing a measurement by which one end of the measurement system is known to be very fast.

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Originally published at eHow, SEP 2011

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Unlike any other light source, a laser produces a single-color beam of light. Saying a laser emits a single color is the same as saying it emits a single wavelength of light. However, a combination of factors — some fundamental to the generation of light — make it impossible for the light to be truly one single wavelength. Instead, each laser emits a range of wavelengths. For ultrastable lasers, that width is very small, and the linewidth requires very accurate measurement.

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Originally published at eHow, SEP 2011

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