Refraction is a change in the direction of a wave as it passes from one medium to another.
Refraction , originating from the Latin word refractio , is the action and consequence of refracting . This verb refers to causing a certain radiation to modify its direction by passing obliquely from one medium to another with a different propagation speed.
Refraction, therefore, is a modification of the direction of a wave when it passes from one medium to another. For this change to occur, the wave must impact in an oblique direction on the surface that separates both media and they must have different refractive indices.
The term refraction is often confused with reflection , which is why it is necessary to slightly define the latter: it is the rebound that a ray experiences when hitting a smooth and polished surface and returning to the previous medium. In this case it is true that: the normal and the incident ray form an angle equal to that which the normal forms with the reflected ray; The normal, the incident ray and the reflected ray are in the same plane.
The refractive index
The ratio between the propagation speeds of a wave in a vacuum and in another medium X is known as the refractive index . The change in direction, on the other hand, can be explained through the so-called Snell's law which, in turn, derives from Fermat's principle .
Fermat's principle , for its part, belongs to the field of optics (the branch of physics that considers light to be a wave, thanks to which it explains certain phenomena that it could not, if it were taken as a ray), and proposes the following: the path that light travels when it propagates between two points is such that it could not be done in a shorter time.
Since this statement does not consider all possibilities, the same principle was expanded to correspond to the discoveries and concepts of modern physics , so that it can currently be explained in the following way: the path that light travels when it propagates between two points is such that the time it takes does not change, regardless of any possible changes that are applied to the trajectory.
The refractive index is the ratio that exists between the propagation speeds of a wave in a vacuum and in another medium.
Snell's law
Snell's law (also known as the Snell-Descartes law ) is a formula used to calculate the angle of refraction of light when it passes through the surface that separates two propagation media (either light or any electromagnetic wave), which must have different refractive indices. It should be noted that the name of the mathematician behind this discovery is Willebrord Snel van Royen, and that the double "l" emerged as a combination of Snel and Wi ll ebrord .
Another statement present in Snell's law is that the result of multiplying the sine of the angle of incidence by the refractive index is constant for all light rays incident on the surface that separates two media.
The most common example of refraction is the phenomenon that occurs when a rod or wooden stick is introduced into a glass full of water. Due to the refraction of light, an optical effect is generated that makes the rod appear broken .
Refraction beyond light
It is important to highlight that refraction is a phenomenon that can be noticed in any wave , beyond light. The waves generated by an earthquake and radio waves are also susceptible to refraction.
Atmospheric refraction , finally, causes the stars to be seen above their real position, since what is observed is modified by the phenomenon of refraction produced by the atmosphere .