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Spatial frequency is a reciprocal length, which can thus be used as a measure of energy, usually of a particle. For example, the reciprocal centimetre, cm −1, is an energy unit equal to the energy of a photon with a wavelength of 1 cm. That energy amounts to approximately 1.24 × 10 −4 eV or 1.986 × 10 −23 J.
For example, a wavenumber in inverse centimeters can be converted to a frequency expressed in the unit gigahertz by multiplying by 29.979 2458 cm/ns (the speed of light, in centimeters per nanosecond); [5] conversely, an electromagnetic wave at 29.9792458 GHz has a wavelength of 1 cm in free space. In theoretical physics, a wave number, defined ...
Because of the identity property of multiplication, multiplying any quantity (physical or not) by the dimensionless 1 does not change that quantity. [5] Once this and the conversion factor for seconds per hour have been multiplied by the original fraction to cancel out the units mile and hour, 10 miles per hour converts to 4.4704 metres per second.
To focus a distant object (s 1 ≈ ∞), the rear principal plane of the lens must be located a distance s 2 = 50 mm from the film plane, so that it is at the location of the image plane. To focus an object 1 m away (s 1 = 1,000 mm), the lens must be moved 2.6 mm farther away from the film plane, to s 2 = 52.6 mm.
A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]
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The mansion has been put on the market at least four other times − in 2008, 2009 and 2011 for $2.3 million and in 2014 for $1.95 million, according to Westword, an independent news publication ...
2.54 cm – 1 inch; 3.08568 cm – 1 attoparsec; 3.4 cm – length of a quail egg [114] 3.5 cm – width of film commonly used in motion pictures and still photography; 3.78 cm – amount of distance the Moon moves away from Earth each year [115] 4.3 cm – minimum diameter of a golf ball [116] 5 cm – usual diameter of a chicken egg; 5 cm ...