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The bevel protractor is used to establish and test angles to very close tolerances. It reads to 5 arcminutes (5′ or 1 / 12 °) and can measure angles from 0° to 450°. The bevel protractor consists of a beam, a graduated dial, and a blade which is connected to a swivel plate (with Vernier scale) by a thumb nut and clamp.
The angle of incidence, in geometric optics, is the angle between a ray incident on a surface and the line perpendicular (at 90 degree angle) to the surface at the point of incidence, called the normal. The ray can be formed by any waves, such as optical, acoustic, microwave, and X-ray. In the figure below, the line representing a ray makes an ...
These postulates are all based on basic geometry that can be confirmed experimentally with a scale and protractor. Since the postulates build upon the real numbers, the approach is similar to a model-based introduction to Euclidean geometry. Birkhoff's axiomatic system was utilized in the secondary-school textbook by Birkhoff and Beatley. [2]
A direct-readout theodolite, manufactured in the Soviet Union in 1958 and used for topographic surveying. A theodolite (/ θ i ˈ ɒ d ə ˌ l aɪ t /) [1] is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes.
[6] [7] [8] These tutorial articles remain useful today, but the primary reference for usage is the 1927 Abney Level Handbook. [3] The Abney level is typically used at the eye height of the surveyor, either hand-held or mounted on a staff at that height. To measure lines on a particular slope, the desired angle or grade is first set on the ...
Dial test indicators, whose tips swing in an arc rather than plunging linearly, usually have spherical tips. This shape gives point contact, allowing for consistent measurements as the tip moves through its arc (via consistent offset distance from ball surface to center point, regardless of ball contact angle with the measured surface). Several ...
The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens, which refracts light rays so that a point source of light is seen as a line or streak of light. [2] Due to the optical properties, the streak of light is seen perpendicular to the axis of the cylinder. [3] Maddox rod and pen torch used in Maddox rod testing
Each point is defined by the effect the optical system has on rays that pass through that point, in the paraxial approximation. The paraxial approximation assumes that rays travel at shallow angles with respect to the optical axis, so that sin θ ≈ θ {\textstyle \sin \theta \approx \theta } , tan θ ≈ θ {\textstyle \tan \theta ...