Search results
Results from the WOW.Com Content Network
The Variable Density Tunnel (VDT) was the second wind tunnel at the National Advisory Committee for Aeronautics Langley Research Center.Proposed by German aerospace engineer, Max Munk, student of Ludwig Prandtl, it was the world's first variable density wind tunnel and allowed for more accurate testing of small-scale models than could be obtained with atmospheric wind tunnels.
Subjective Refraction is a technique to determine the combination of lenses that will provide the best corrected visual acuity (BCVA). [1] It is a clinical examination used by orthoptists , optometrists and ophthalmologists to determine a patient's need for refractive correction, in the form of glasses or contact lenses.
A duochrome test is a test commonly used to refine the final sphere in refraction (undercorrection and overcorrection), which makes use of the longitudinal chromatic aberration of the eye. Because of the chromatic aberration of the eye, the shorter wavelengths (green) are focused in front of the longer red wavelengths.
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.
By measuring this zone, the autorefractor can determine when a patient's eye properly focuses an image. The instrument changes its magnification until the image comes into focus. The process is repeated in at least three meridians of the eye and the autorefractor calculates the refraction of the eye, sphere, cylinder and axis.
The test is based on the principle of diplopic projection. [1] Dissociation of the deviation is brought about by presenting a red line image to one eye and a white light to the other, while prisms are used to superimpose these and effectively measure the angle of deviation (horizontal and vertical).
A pinhole occluder is an opaque disk with one or more small holes through it, used by ophthalmologists, orthoptists and optometrists to test visual acuity. The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing the effects of refractive errors such as myopia. Because light passes only through the center of the ...