Is total internal reflection 90 degrees?

Total Internal Reflection

Total internal reflection is a phenomenon that occurs when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected. The critical angle is the angle of incidence above which the total internal reflection occurs.

It is important to note that total internal reflection is not a 90-degree phenomenon. The angle of incidence at which total internal reflection occurs, known as the critical angle, depends on the refractive indices of the two media involved. The critical angle can be calculated using Snell's law, which relates the angles of incidence and refraction to the refractive indices of the two media.

For total internal reflection to occur, the following conditions must be met:

• The wave must travel from a medium with a higher refractive index to a medium with a lower refractive index.
• The angle of incidence must be greater than the critical angle for the media interface.

When these conditions are satisfied, the wave is completely reflected back into the medium from which it came, with no transmission into the second medium. This principle is utilized in various applications, including optical fibers, where it enables the confinement of light within the fiber, allowing for efficient transmission of signals over long distances.