THE reflectiontotal is an optical phenomenon that occurs when light incident on a surface that separates two media, from the largest to the smallest refractive index, is fully reflected, remaining in the middle of origin. This phenomenon only occurs if the angle of incidence is greater than the so-called limit angle.
limit angle
O limit angle is the smallest angle of incidence needed for the angle of refraction of a ray of light, in the passage from a medium with a higher to another with a lower refractive index, is 90º.
The refractive index of medium 2 is greater than the refractive index of medium 1. So, through the Snell-Descartes' law, it is possible to determine the limit angle L.
The sine value of the limiting angle is defined by the ratio of the smallest to the largest refractive index.
full light reflection
If the angle of incidence of a ray of light is greater than the limit angle, the ray of light undergoes total reflection.
Note that the incidence angle of the green light ray in the image above is larger than the threshold angle, so the light ray has been fully reflected, remaining in the middle 2.
Total reflection effects
→ Mirages
On days of intense heat and very sunny, it is possible to observe the apparent formation of water puddles on the hot asphalt. The image seen from distant points on the asphalt is amirage, resulting from the phenomenon of total reflection.
The various layers of air above the asphalt have different temperatures. The closer to the ground, the higher the air temperature. THE densityof the warmer air layers is smaller and, therefore, the refractive index of the air masses decreases as they get closer to the ground. Therefore, sunlight undergoes numerous refractions as it approaches the ground. Thus, at certain points, the angle of incidence of the sun's rays becomes greater than the limit angle, causing the total reflection of light. The rays that result from the total reflection reach the eyes of a possible observer and give the sensation of the formation of water puddles.
→ Optical fibers
Atoptical fibers are filaments capable of carrying light and are used for image diagnosis and data transmission.
Optical fibers are made of materials with different refractive indices, which guarantees the occurrence of the phenomenon of total reflection and enables the transmission of light rays.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-reflexao-total.htm
