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Hence an angle of 1.2 radians would be written today as 1.2 rad; archaic notations include 1.2 r, 1.2 rad, 1.2 c, or 1.2 R. In mathematical writing, the symbol "rad" is often omitted. When quantifying an angle in the absence of any symbol, radians are assumed, and when degrees are meant, the degree sign ° is used.
The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
Abbreviations In radians, approx. Degree 1 / 360 turn ° Degree: deg: 17.453 2925 mrad: Arcminute 1 / 60 degree ′ Prime: arcmin, amin, am, MOA: 290.888 2087 μrad: Arcsecond 1 / 60 arcminute = 1 / 3600 degree ″ Double prime: arcsec, asec, as: 4.848 1368 μrad: Milliarcsecond 0.001 arcsecond = 1 / 3600000 ...
≈ 0.157 080 × 10 −3 rad: centesimal second of arc" ≡ 1 ⁄ 10 000 grad ≈ 1.570 796 × 10 −6 rad: degree (of arc) ° ≡ 1 ⁄ 360 of a revolution ≡ π ⁄ 180 rad ≈ 17.453 293 × 10 −3 rad: grad; gradian; gon: grad ≡ 1 ⁄ 400 of a revolution ≡ π ⁄ 200 rad ≡ 0.9° ≈ 15.707 963 × 10 −3 rad: octant: ≡ 45° ≈ 0. ...
Solid angles can also be measured in square degrees (1 sr = (180/ π) 2 square degrees), in square arc-minutes and square arc-seconds, or in fractions of the sphere (1 sr = 1 / 4 π fractional area), also known as spat (1 sp = 4 π sr). In spherical coordinates there is a formula for the differential,
Units are represented in UCUM with reference to a set of seven base units. [5] The UCUM base units are the metre for measurement of length, the second for time, the gram for mass, the coulomb for charge, the kelvin for temperature, the candela for luminous intensity, and the radian for plane angle.
For an exposure of 1 roentgen by gamma rays with an energy of 1 MeV, the dose in air will be 0.877 rad, the dose in water will be 0.975 rad, the dose in silicon will be 0.877 rad, and the dose in averaged human tissue will be 1 rad. [10] "rad" stands for radiation absorbed dose. [4]