Refractive index - Wikipedia
In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refracted, when entering a material.
List of refractive indices - Wikipedia
In general, an index of refraction is a complex number with both a real and imaginary part, where the latter indicates the strength of absorption loss at a particular wavelength—thus, the imaginary part is sometimes called the extinction coefficient.
Negative refraction - Wikipedia
Negative refraction occurs at interfaces between materials at which one has an ordinary positive phase velocity (i.e., a positive refractive index), and the other has the more exotic negative phase velocity (a negative refractive index).
Optical path length - Wikipedia
It is calculated by taking the product of the geometric length of the optical path followed by light and the refractive index of the homogeneous medium through which the light ray propagates; for inhomogeneous optical media, the product above is generalized as a path integral as part of the ray tracing procedure.
Gradient-index optics - Wikipedia
Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradient of the refractive index of a material. Such gradual variation can be used to produce lenses with flat surfaces, or lenses that do not have the …
Phase-contrast imaging - Wikipedia
It measures differences in the refractive index of different materials to differentiate between structures under analysis. In conventional light microscopy, phase contrast can be employed to distinguish between structures of similar transparency, and to examine crystals on the basis of their double refraction. This has uses in biological ...
Kramers–Kronig relations - Wikipedia
The Kramers–Kronig relations are used to relate the real and imaginary portions for the complex refractive index ~ = + of a medium, where is the extinction coefficient. [12] Hence, in effect, this also applies for the complex relative permittivity and electric susceptibility .
Snell's law - Wikipedia
In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics to find the refractive index of a material. The law is also satisfied in meta-materials, which allow light to be bent "backward" at a negative angle of refraction with a negative refractive index.
Cauchy's equation - Wikipedia
In optics, Cauchy's transmission equation is an empirical relationship between the refractive index and wavelength of light for a particular transparent material. It is named for the mathematician Augustin-Louis Cauchy, who originally defined it in 1830 in his article "The refraction and reflection of light". [1]
Refraction - Wikipedia
A pencil part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y. Refraction occurs when light goes through a water surface since water has a refractive index of 1.33 and air has a refractive index of about 1.