Discover the expert in you.
Discover the expert in you.
Radiation is present all around us. It comes from the sun, machines, chemicals, the earth and naturally occurring substances. Most sources of radiation do not cause harm and should not cause any concern, though some types of radiation can be very dangerous. Scientists use very sensitive instruments and very precise units to measure radiation.
Chemists working in the metric system have a variety of units at their disposal to describe chemical quantities. One common unit is the mole, which stands for 6.02 x 10^23 atoms or molecules of a substance. The metric system uses a series of standard prefixes to indicate magnitude and the prefix "pico" means there are 1 x 10^12 picomoles (pmol) in a mole. Grams (g) are a standard metric unit of mass and a milligram (mg) is one thousandth of a gram.
Chemists use a wide assortment of units to measure the quantities of chemical substances. One such unit is the mole, which stands for 6.02 x 10^23 atoms or molecules. Since moles are a metric system unit, the standard metric prefixes can be used with them to indicate magnitude. A picomole (pmol) is a mole multiplied by 10^-12 and so is a very small quantity. Chemists also use grams to measure chemical mass and, sometimes, use nanograms (ng) to describe very small amounts, where one ng is a gram multiplied by 10^-9. You can convert between pmol and ng using the…
Zero-point energy is the lowest possible energy an object can have. The zero-point energy is a concept that comes from quantum mechanics, as only objects governed by the laws of quantum mechanical (such as extremely small objects) can ever attain this ground-state energy. A way to illustrate the concept of zero-point energy is through the use of a quantum harmonic oscillator, which will always some energy.
Radioactive substances are unstable. Carbon-14, for example, has a half-life of approximately 5,700 years. This means that if you put two ounces of carbon-14 in your pocket today, you'll find one ounce of carbon-14 in your pocket 5,700 years from now. Scientists use the Curie (Ci) to quantify the radioactive activity of a substance. One Curie equals 2.22 x 10^12 disintegrations per minute (dpm). A disintegration is a single photon, or particle, released by the radioactive substance as the substance decays. The millicurie (mCi) is the most commonly used Curie unit in scientific laboratories.
Calculations dealing with the physics of light waves are sometimes easier to solve if you use the frequency of light instead of its wavelength. As Albert Einstein stated in his 1905 paper on the Special Theory of Relativity, light always has the same speed: 300,000,000 meters per second in vacuum. This means you can convert from nanometers of wavelength to frequency easily. Simply divide the speed by the wavelength in meters. Since your wavelength is in nanometers, multiply by 1,000,000,000 to get the result in hertz.
The Si unit of mass is the gram, shortened to the lowercase letter "g." Scientists often need a way express small fractions of a gram without using decimal values in which the number of zeros may be misinterpreted. Units such as the nanogram and picogram meet this need. For example, 1 nanogram -- 1 ng -- is easier to read than 0.000 000 001 g. Likewise, 1 picogram -- 1 pg -- is easier to understand than 0.000 000 000 001 grams. Converting between picograms and nanograms is simple.
When you count from zero to 10 using your fingers, you are using a decimal system: 10 is the basis of this system. For example, the number 377 in the decimal system represents three units of 100 (10 x 10); seven units of tens (10 x 1); and seven units of ones. The hexadecimal system is the same as the decimal system, except it uses units of 16 for counting rather than units of 10. If you have a frequency given in decimal Hertz, you can easily convert your decimal Hertz to hexadecimal Hertz.
A nanometer is one of the smallest units of measurements. Scientists use it to measure extremely tiny objects. One billion nanometers comprise a meter, so converting from meters, centimeters or millimeters down to nanometers is a simple calculation. To calculate the length, width or height of an object in nanometers, it is necessary to convert down from a larger unit because 1 nanometer is too small for the human eye to see.
A hertz (Hz) is a unit of frequency equal to one cycle per second in the metric system. Car enthusiasts measure the rate at which an engine turns in revolutions per minute (rpm). You won't often see engine revolutions measured in hertz, but if you do, you can quickly convert hertz to rpm by simple multiplication.
The American Radio Relay League (ARRL) is an organization of amateur radio operators who correspond on a variety of frequencies. Radio waves can be measured by frequency in hertz (cycles per second) or by wavelength in meters. You can convert a frequency to a wavelength by simple multiplication.
A hertz (Hz) is a frequency unit in the metric system equal to one cycle per second. The metric prefix "kilo" denotes a thousand; hence, a kilohertz (kHz) equals 1,000 hertz. These units are both used to measure the frequency of radio waves, sound waves and alternating-current electricity, among other things. It's simple to convert kilohertz to hertz. You just need to multiply by a constant.
Hertz and RPM (revolutions per minute) both measure frequency, which is how many times something occurs in a given time period. Hertz is the SI unit for cycles per second of a wave or revolutions per second for a wheel, but some problems will use the RPM for the revolutions or repetitions per minute. Converting between these two requires a simple calculation, taking into account that 1 hertz equals 60 RPM.
The nucleus of an atom is a charged particle -- and it spins, producing a small magnetic field around itself. When many nuclei of the same atom are placed in an external magnetic field, about half of the nuclei align with the field and the other half align against the field, depending on their energy state. Energy is proportional to frequency. The dividing frequency (energy) where they flip one way or the other is an important property of the atom, and it is where we observe nuclear magnetic resonance (NMR). When you introduce several of another atom's nuclei into the…
The basic unit of frequency is the hertz, which equals one cycle per second. The inverse of frequency is the period, or the time it takes for one cycle to occur. For example, a frequency of 100 hertz has a period equal to 1/100 second, or 0.01 second. A nanosecond (ns) is one billionth of a second. You can determine the frequency that has a period of 8 ns by finding its inverse.
Hertz, the unit of frequency as defined by the International System of Units, or "SI," represents the number of times per second a signal oscillates. If a given wave is moving, such as light, the path can be thought of as a point traversing a sine wave. The absolute difference between the high peaks and low peaks is the amplitude; the distance between the peaks is the wavelength. As frequency changes so does the wavelength. All that is required to make the conversion between frequency and wavelength is the speed of the propagating signal. The speed of light in a…
You can convert the frequency of a wave in Hertz (Hz) to the number of pulses per foot--only if you know the speed of the wave. This is because frequency is the measure of pulses (or cycles) per second, but it tells you nothing about the length of each pulse, which is a wave property known as "wavelength." You can obtain the wavelength of a wave by dividing the wave's speed by its frequency. Once you have the wavelength, calculating the number of pulses per foot is easy. Luckily, the speeds of many types of waves, like light and sound,…
Hertz, the unit of measurement for frequency, represents the number of times a pattern repeats itself over a period of one second. Radians per second, also a unit of measurement for frequency, represents the number of radians that a pattern traverses over a period of one second. Physicists as well as electrical and mechanical engineers often must convert frequency from Hertz to radians per second to solve a variety of complex problems. Also, many scientific calculators require that frequency data be entered as radians per second.
Frequency in Hertz refers to the number of cycles something occurs each second, i.e., the turn of a wheel or the movement of a wave. Radians per second equal twice the frequency in Hertz times "pi" (3.14), but you can also take this relation and find the number of Hertz from the radians per second.
Frequency characterizes any periodic or cyclical process, and specifies a number of cycles that occur in a given period of time, whether in one second or in one hour. The International System of Units (SI) defines "hertz," abbreviated "Hz," as a unit of frequency that refers to the number of periodic events per one second. However, rotation speeds or machinery vibrations are often measured using a different unit: cycles-per-minute, which is abbreviated as "CPM."
Frequency describes the time it takes for the motion of an object to repeat itself. Its units are in hertz, which is defined as one oscillation per second. A radian is a unit used to indicate the angle an object is at, or how far it has rotated. One radian is 360 degrees divided by 2Pi, and it is dimensionless. Therefore, radians cannot be converted to hertz. However, a radian per second, which is the angular speed or frequency, may be, because it specifies the rate of change of the angular position of the object as it moves.
Frequency is a way to describe oscillatory motion, such as that by a particle or wave. It describes the time it takes for a motion to repeat itself. It is measured in hertz, which is one oscillation per second or 1/second. "Rpm" is short for revolutions per minute, and it denotes circular motion, or the rotations completed by an object around an axis. For motors, it tells how quickly they can rotate when not under a load. The frequency of a motor can be converted to rpm and vice versa.
