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Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1. Since the phase velocity is lower in the second medium ( v 2 < v 1 ), the angle of refraction θ 2 is less than the angle of incidence θ 1 ; that is, the ray in the higher-index medium is closer to the normal.
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°. The refractive indices of water and air are approximately 1.333 and 1, respectively, so Snell's law gives us the relation
Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]
As an example, water has a refractive index of 0.999 999 74 = 1 − 2.6 × 10 −7 for X-ray radiation at a photon energy of 30 keV (0.04 nm wavelength). [21] An example of a plasma with an index of refraction less than unity is Earth's ionosphere.
The ordinary law of refraction was at that time attributed to René Descartes (d. 1650), who had tried to explain it by supposing that light was a force that propagated instantaneously, or that light was analogous to a tennis ball that traveled faster in the denser medium, [44] [45] either premise being inconsistent with Fermat's.
For example, the speed of light in water is about 3/4 of that in vacuum. ... Refraction is the bending of light rays when passing through a surface between one ...
Looming of the Canadian coast as seen from Rochester, New York, on April 16, 1871. Looming is the most noticeable and most often observed of these refraction phenomena. It is an abnormally large refraction of the object that increases the apparent elevation of the distant objects and sometimes allows an observer to see objects that are located below the horizon under normal conditions.
Common optical phenomena are often due to the interaction of light from the Sun or Moon with the atmosphere, clouds, water, dust, and other particulates. One common example is the rainbow, when light from the Sun is reflected and refracted by water droplets.