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A Guide to Types of Whatman Filter Paper Grades Professional

منذ أسبوعين Multimedia Saïda   27 الآراء

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A Guide to Types of Whatman Filter Paper Grades

A device that transmits part of a received signal and rejects the rest. The signal may be in the form of a beam of light or other radiation or may be an electrical signal. Optical, ultraviolet, and infrared filters are dyed plastic or gelatin, glass or glasslike substances, or confined liquids, all of which absorb incident radiation except for a relatively narrow band of wavelengths. Such filters are used in astronomical photometry, especially in measurements of magnitudes; transmitting bands typically 100 nanometers wide, they are termed broadband filters. Much narrower wavelength bands, of maybe 1 nm, can be obtained with interference and birefringent filters.

Electrical filters are devices whose attenuation varies with frequency. Filters that allow low or high frequencies to pass without serious attenuation are called low-pass and high-pass filters, respectively. A filter that allows only a limited range of frequencies through is a band-pass filter while its converse is a band-stop filter. See also bandwidth.

The term “filter” is also applied to a number of other devices, which are not discussed in the present article. For example, devices that pass or reject acoustic or electromagnetic waves of certain frequencies are called filters, and the term is sometimes applied to devices that separate polymer ions into fractions or remove salts from solutions by means of ion exchangers.

According to the nature of the heterogeneous system, a distinction is made between liquid filters, which are used to LTE filter suspensions, and gas filters, which are used to separate out aerosols and to purify gases. The simplest filter is a vessel that is divided into two parts by a filter medium. A pressure difference is established across the filter to force the liquid or gas through the filter medium, which holds back the solid particles.