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2 + 2 = 5 or two plus two equals five is a mathematical falsehood which is used as an example of a simple ... and the title of the imagist art manifesto 2 x 2 = 5 ...
Power of two. A power of two is a number of the form 2n where n is an integer, that is, the result of exponentiation with number two as the base and integer n as the exponent. Powers of two with non-negative exponents are integers: 20 = 1, 21 = 2, and 2n is two multiplied by itself n times. [1][2] The first ten powers of 2 for non-negative ...
f-number. Diagram of decreasing apertures, that is, increasing f-numbers, in one-stop increments; each aperture has half the light-gathering area of the previous one. An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the ...
An illustration of light sources from magnitude 1 to 3.5, in 0.5 increments. In astronomy, magnitude is a measure of the brightness of an object, usually in a defined passband. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus. Magnitude values do not have a unit.
The basic unit of insulation coefficient is the RSI, (1 m 2 ⋅K/W). 1 tog = 0.1 RSI. There is also a US clothing unit, the clo, equivalent to 0.155 RSI or 1.55 tog, described in ASTM D-1518. [3] A tog is 0.1⋅m 2 ⋅K/W. In other words, the thermal resistance in togs is equal to ten times the temperature difference (in °C) between the two ...
A dioptre (British spelling) or diopter (American spelling), symbol dpt or D, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m−1. It is normally used to express the optical power of a lens or curved mirror, which is a physical quantity equal to the reciprocal of the focal length ...
The Mach number is named after the physicist and philosopher Ernst Mach [3] according to a proposal by the aeronautical engineer Jakob Ackeret in 1929. [4] The word Mach is always capitalized since it derives from a proper name, and since the Mach number is a dimensionless quantity rather than a unit of measure, the number comes after the word Mach; the second Mach number is Mach 2 instead of ...
1 / 10 bel. The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 10 1/10 (approximately 1.26) or root-power ratio of 10 1/20 (approximately ...