What is the critical angle?

The critical angle is defined as the minimum angle of incidence at which total internal reflection occurs when light travels from a denser medium to a less dense medium. When light hits the boundary between these two mediums at angles equal to or greater than this critical angle, it no longer refracts into the second medium but is completely reflected back into the first medium. This phenomenon is fundamental to the operation of optical fibers and various optical devices, as it allows light to be contained within a medium, enabling efficient transmission with minimal loss.

Understanding the critical angle is essential in optics, as it determines the threshold for reflection versus refraction. Therefore, being familiar with this concept helps in comprehending various optical applications and principles related to light behavior at interfaces.