1. Total Internal Reflection:
Total internal reflection occurs when light traveling through a medium reaches a boundary with another medium and is entirely reflected back into the same medium instead of being transmitted into the second medium. This phenomenon happens when the angle of incidence of the light ray is larger than the critical angle for the boundary between the two media.
To observe total internal reflection, the light must be traveling from a medium with a higher refractive index (such as glass or water) towards a medium with a lower refractive index (such as air). When the angle of incidence exceeds the critical angle, the light undergoes complete reflection, with no portion of the light being transmitted into the second medium.
Total internal reflection has various practical applications, such as in fiber optics communication systems, where light signals are transmitted through optical fibers using total internal reflection. It is also responsible for phenomena like mirages and diamond sparkle, where light undergoes multiple reflections within a medium before reaching the observer's eyes.
2. Critical Angle:
The critical angle is a specific angle of incidence that marks the threshold for total internal reflection to occur at the boundary between two different transparent media. It is the angle at which light traveling from a medium with a higher refractive index to a medium with a lower refractive index will result in total internal reflection.
Mathematically, the critical angle (θc) can be calculated using Snell's law, which relates the angles and refractive indices of the two media:
θc = sin^(-1)(n2 / n1)
where n1 is the refractive index of the first medium (where the incident light is coming from), and n2 is the refractive index of the second medium (where the light is approaching).
If the angle of incidence is greater than the critical angle, total internal reflection occurs. If the angle of incidence is smaller than the critical angle, the light is partially refracted into the second medium and partially reflected.
Understanding the critical angle is crucial for various optical applications, such as designing lenses, determining the acceptance angles of optical fibers, and understanding the behavior of light at boundaries between different media.