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An arc of a circle with the same length as the radius of that circle corresponds to an angle of 1 radian. A full circle corresponds to a full turn, or approximately 6.28 radians, which is expressed here using the Greek letter tau (τ). Some special angles in radians, stated in terms of 𝜏. A comparison of angles expressed in degrees and radians.
A half-turn may refer to: One half of a full turn, an angle measure equivalent to 180 degrees or π radians Considering only points in a plane, a half turn is equivalent to a point reflection; Pi (π), a mathematical constant representing a half-turn in radians; A U-turn: a driving maneuver used to reverse direction
An angle equal to 0° or not turned is called a zero angle. [10] An angle smaller than a right angle (less than 90°) is called an acute angle [11] ("acute" meaning "sharp"). An angle equal to 1 / 4 turn (90° or π / 2 radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or ...
The largest possible angle of incidence which still results in a refracted ray is called the critical angle; in this case the refracted ray travels along the boundary between the two media. Refraction of light at the interface between two media. For example, consider a ray of light moving from water to air with an angle of incidence of 50°.
If every internal angle of a simple polygon is less than a straight angle (π radians or 180°), then the polygon is called convex. In contrast, an external angle (also called a turning angle or exterior angle) is an angle formed by one side of a simple polygon and a line extended from an adjacent side. [1]: pp. 261–264
Thus, for example, the sum of phase angles 190° + 200° is 30° (190 + 200 = 390, minus one full turn), and subtracting 50° from 30° gives a phase of 340° (30 − 50 = −20, plus one full turn). Similar formulas hold for radians, with 2 π {\displaystyle 2\pi } instead of 360.
A full-wave plate introduces a phase difference of exactly one wavelength between the two polarization directions, for one wavelength of light. In optical mineralogy, it is common to use a full-wave plate designed for green light (a wavelength near 540 nm). Linearly polarized white light which passes through the plate becomes elliptically ...
The vanes rotate when exposed to light, with faster rotation for more intense light, providing a quantitative measurement of electromagnetic radiation intensity. The reason for the rotation was a cause of much scientific debate in the ten years following the invention of the device, [ 1 ] [ 2 ] but in 1879 the currently accepted explanation for ...