The becquerel (symbol Bq) is the SI derived unit The International System of Units specifies a set of seven base units from which all other units of measurement are formed. These other units are called SI derived units and are also considered part of the standard of radioactivity Radioactive decay is the process by which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter nuclide. For example: a carbon-14 atom emits radiation. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus The nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford decays per second The second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock. The Bq unit is therefore equivalent to s The second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock−1. The becquerel is named for Henri Becquerel Antoine Henri Becquerel was a French physicist, Nobel laureate, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics (along with Marie Curie and Pierre Curie who had found additional radioactive elements), who shared a Nobel Prize The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. They were established in 1895 by the Swedish chemist Alfred Nobel, the inventor of dynamite. The prizes in Physics, Chemistry, Physiology or Medicine, Literature, and Peace were first awarded in 1901. The with Pierre Pierre Curie was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate. In 1903 he received the Nobel Prize in Physics with his wife, Maria Skłodowska-Curie, and Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the and Marie Curie for their work in discovering radioactivity.
In a fixed mass of radioactive material, the number of becquerels changes with time. Therefore, a sample radioactive decay rate is always stated with a timestamp for short-lived isotopes Isotopes are different types of atoms of the same chemical element, each having a different number of neutrons. In a corresponding manner, isotopes differ in mass number (or number of nucleons) but never in atomic number. The number of protons (the atomic number) is the same because that is what characterizes a chemical element. For example,, sometimes after adjustment to some specific date of interest (in the past or in the future). For example, one might quote a ten-day adjusted figure, that is, the amount of radioactivity that will still be present ten days in the future. This can de-emphasize short-lived isotopes.
SI The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science uses the becquerel rather than the second for the unit of activity measure to avoid dangerous mistakes: a measurement in becquerels is proportional to activity, and thus a more dangerous source of radiation gives a higher reading. A measurement in seconds is inversely proportional.
The becquerel can be used for the frequency of aperiodic or stochastic events; that is, events which occur randomly and cannot be exactly predicted. For periodic events, the hertz The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of sine wave, particularly those used in radio and audio applications, which is also defined as s−1, is used as a unit.
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Prefixes
As any SI unit, Bq can be prefixed The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decimal multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol. The SI prefixes are standardized by the International; commonly used multiples are kBq (kilobecquerel, 103 Bq), MBq (megabecquerel, 106 Bq), GBq (gigabecquerel, 109 Bq), TBq (terabecquerel, 1012 Bq), and PBq (petabecquerel, 1015 Bq). For practical application, 1 Bq is a small unit; therefore, the prefixes are common. For example, natural potassium Potassium is the chemical element with the symbol K (Latin: kalium, from Arabic: القَلْيَه al-qalyah "plant ashes" cf. Alkali from the same root, more commonly known in Modern Standard Arabic as بوتاسيوم ‹bwtasywm›), atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash. Elemental (40K) in a typical human body produces 4,000 disintegrations per second (i.e., 4 kBq of activity).[1] The nuclear explosion During the final stages of World War II in 1945, the United States conducted two atomic bombings against Japan in the cities of Hiroshima and Nagasaki in Hiroshima Hiroshima ( listen (help·info)) is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest island of Japan. It became the first city in history destroyed by a nuclear weapon when the United States of America dropped an atomic bomb on it at 8:15 A.M. on August 6, 1945, near the end of World (14 kt TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 giga or 59 TJ) is estimated to have produced 8×1024 Bq.[2]
Bq versus counts per second
When measuring radioactivity of a sample with a detector, a unit of "counts per second" (cps) or "counts per minute" (cpm) are often used. These units can be converted to the absolute activity of the sample in Bq if one applies a number of significant conversions, e.g., for the radiation background, for the detector efficiency, for the counting geometry, for self-absorption of the radiation in the sample.
Relationship to the curie
The curie This is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. The curie has since been replaced by an SI derived unit, the becquerel , which equates to one decay per second. Therefore: (Ci) is an older, non-SI unit of radioactivity.
The conversion factors are:
- 1 Ci = 3.7×1010 Bq
and
- 1 Bq = 2.70×10−11 Ci
Definition
1 Bq = 1 s−1
This SI The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science unit is named after Henri Becquerel Antoine Henri Becquerel was a French physicist, Nobel laureate, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics (along with Marie Curie and Pierre Curie who had found additional radioactive elements). As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol A symbol is something such as an object, picture, written word, sound, or particular mark that represents something else by association, resemblance, or convention. For example, a red octagon may be a symbol for "STOP". On maps, crossed sabres may indicate a battlefield. Numerals are symbols for numbers . All language consists of symbols is uppercase Capital letters or majuscules are the larger of two type faces in a script. In the Roman alphabet they are A, B, C, D, etc. They are also called capitals (caps) or upper case (uppercase). The latter name comes from the antique age of setting type for printing presses, when printers kept the type for these letters in the upper drawers of a desk or (Bq). When an SI unit is spelled out in English, it should always begin with a lowercase Lower case , minuscule, or small letters are the smaller form of letters, as opposed to upper case or capital letters, as used in European alphabets (Greek, Latin, Cyrillic, and Armenian). For example, the letter "a" is lower case while the letter "A" is upper case letter (becquerel), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature interval (a difference between two temperatures" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.
References
- ^ Radioactive human body — Harvard University Natural Science Lecture Demonstrations
- ^ Michael J. Kennish, Pollution Impacts on Marine Biotic Communities , CRC Press, 1998, p. 74. ISBN 9780849384288.
External links
- Derived units on the International Bureau of Weights and Measures The International Bureau of Weights and Measures , is an international standards organisation, one of three such organisations established to maintain the International System of Units (SI) under the terms of the Metre Convention (Convention du Mètre). The organisation is usually referred to by its French initialism, BIPM (BIPM) web site
Categories: SI derived units | Units of radioactivity | Units of frequency
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Sat, 30 Jun 2007 09:57:16 GM
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