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What is Total Internal Reflection or TIR
The Total Internal Reflection is an optical characteristic of light where a beam of light propagates from an optically denser medium (e.g. water) into an optically rarer medium(e.g. air) at an angle of incidence greater than the critical angle for the two media separated at the interface is reflected once again into the same medium.
What causes Total Internal Reflection or TIR
We are innately familiar with the concept that some rays are reflected, and some are refracted when a light ray passes from an optically rarer medium to an optically denser medium. But what if the light propagates from a denser medium to a rarer medium? Let’s find it out.
When a light ray propagates from an optically denser medium ( having a larger refractive index) to an optically rarer medium (having a comparatively lower refractive index), the angle of refraction( r) is comparatively greater than the corresponding angle of incidence (i), then from implications of Snell’s Law, we hereby obtain that
Let us suppose we gradually keep increasing the incidence angle (i). In that case, the corresponding angle of refraction (r) will also increase accordingly and at a particular stage, the angle of refraction,r will become 90°. This will be the critical point, also known as the critical angle, where the transition takes place for the given pair of media. If the angle of incidence is increased further, then there is no angle of refraction which can further satisfy the principle of Snell’s Law. As a result, the ray will not be refracted to the next medium and instead, the entire light beam will then be reflected back into the same medium. This optical phenomenon is stated as Total Internal Reflection or TIR.
Some Important Applications or Common Real-time Observations of Total Internal Reflection
Mirage
The sighting of inverted images on hot, still summer days is called mirage as it gives an illusion of water, especially in deserts. The phenomenon is on account of the combined effect of:
Successive refraction of various layers of air having different values of Refractive index and
Total Internal Reflection (TIR)
Sparkling of Diamonds
The ordinarily high refractive index of diamonds prompts its slight critical angle in the air of 24.5°. Diamonds are handily cut with numerous features so that a large part of the incident light goes through various total internal reflections inside the diamond before passing out again in the air. Many of the beams incident on the diamond from above are reflected back. To keep diamond rings sparkling, the lower part of the diamond should be kept clean, so the sharp change in refractive index from the diamond to air is maintained and the critical angle is kept low.
Optical Fibre Cables
Total Internal Reflection is the essential part of physics known as fibre optics.
An optical fibre is an exceptionally meagre fibre made of glass or plastic having a span of a micrometre or 10-6 m. A heap of such slight filaments form a light pipe.
Light pipes utilising optical strands might be utilised to see places that are challenging to arrive at, such as within a human body. The other significant use of fibre optics is to send correspondence signals through light pipes.
Note: The fibre in the light pipes should be optically protected from one another. This is generally finished by covering every fibre with a material that has a refractive record, not exactly that of the fibre.
Conclusion
Total Internal Reflection is part of our daily life and has many applications and much significance. It happens because of the distinction in the refractive records of two mediums that are packaged together and, consequently, light snares in the middle of them because of some particular point of occurrences (more noteworthy than an essential point). Along these lines, it is truly critical to have a profound thought regarding the total internal reflection to comprehend the fundamental standards of different things such as optical strands, endoscopy, and an assortment of routine things. Total inside reflection subsequently shapes the premise of various facets that assist in clinical science, telecom, etc.
