Question: The Term Angle Of Deviation Is Used In Reference To
Answer: (2) Prisms
It is the difference between the angle of incidence and angle of refraction, when a ray of light is refracted when passing from one medium to another (of different refractive index). However, if the ray is passing through a prism or a water drop, it gets refracted twice; one entering into prism and second time when it exits the medium. In such cases of double deflection, the angle of incidence is the sum of these two angles.
White light consists of all frequencies (Color is decided by the frequency of light; Red has lowest frequency while violet has highest frequency). According to Snell’s Law, red light gets deviated least, while violet is deflected by the largest angle. So when a white light passes through a prism, all frequencies are deviated at different angles and we get a spectrum of light.
Red light is deviated least. This explains why danger signs, beacons, etc atop the towers are of red color. So that the flights and vehicles can easily see the danger signals, even from a far distance.
Total Internal Reflection
When the angle of incidence exceed a minimum angle (called critical angle), the incident ray, instead of getting refracted, reflects from the surface. Fiber optic cable used in communication works on the principle of total internal reflection.