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In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for the diameter of a sphere . In more modern usage, the length of a diameter is also called the diameter.
1 μm — edge of cube of volume 10 −18 m 3 (one femtolitre) 1–10 μm — diameter of a typical bacterium. 1.55 μm — wavelength of light used in optical fibre. 3–4 μm — size of a typical yeast cell. 5 μm — length of a typical human spermatozoon 's head [22] 6 μm — anthrax spore.
The nanometre ( SI symbol: nm) is a unit of length in the metric system equal to 10−9 metres ( 1 1 000 000 000 m = 0.000 000 001 m ). To help compare different orders of magnitude, this section lists lengths between 10 −9 and 10 −8 m (1 nm and 10 nm). 1 nm – diameter of a carbon nanotube.
Distance (graph theory) In the mathematical field of graph theory, the distance between two vertices in a graph is the number of edges in a shortest path (also called a graph geodesic) connecting them. This is also known as the geodesic distance or shortest-path distance. [1] Notice that there may be more than one shortest path between two ...
Semicircle: one of the two possible arcs determined by the endpoints of a diameter, taking its midpoint as centre. In non-technical common usage it may mean the interior of the two-dimensional region bounded by a diameter and one of its arcs, that is technically called a half-disc. A half-disc is a special case of a segment, namely the largest one.
For example, if a circle has twice the diameter of another circle, it will also have twice the circumference, preserving the ratio . This definition of π implicitly makes use of flat (Euclidean) geometry ; although the notion of a circle can be extended to any curve (non-Euclidean) geometry , these new circles will no longer satisfy the ...
This dimension is a matter of convention—for example radius and diameter are equally valid to describe spheres or circles, but one is chosen by convention. For aircraft or ships, the length or width can be used. For flow in a pipe, or for a sphere moving in a fluid, the internal diameter is generally used today.
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. [1] Aerosols can be generated from natural or human causes. The term aerosol commonly refers to the mixture of particulates in air, and not to the particulate matter alone. [2] Examples of natural aerosols are fog, mist or dust.