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Special relativity. The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour).
Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by ...
The lumen (symbol: lm) is the unit of luminous flux, a measure of the perceived power of visible light emitted by a source, in the International System of Units (SI). ). Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to ...
The litre ( British English spelling) or liter ( American English spelling) (SI symbols L and l, [ 1] other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm 3 ), 1000 cubic centimetres (cm 3) or 0.001 cubic metres (m 3 ). A cubic decimetre (or litre) occupies a volume of 10 cm × 10 cm × 10 cm (see figure) and ...
A light-year, alternatively spelled light year ( ly or lyr[ 3] ), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km ( Scientific notation: 9.4607304725808 × 10 12 km), which is approximately 5.88 trillion mi.
3LR12 (4.5-volt), D, C, AA, AAA, AAAA (1.5-volt), A23 (12-volt), PP3 (9-volt), CR2032 (3-volt), and LR44 (1.5-volt) batteries. This is a list of the sizes, shapes, and general characteristics of some common primary and secondary battery types in household, automotive and light industrial use. The complete nomenclature for a battery specifies ...
The reputed quart was a measure equal to two-thirds of an imperial quart (or one-sixth of an imperial gallon), at about 0.7577 liters, which is very close to one US fifth (0.757 liters). The reputed quart was previously recognized as a standard size of wine bottle in the United Kingdom, and is only about 1% larger than the current standard wine ...
CGS units. 10−4 ph. The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). [ 1][ 2] It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.