In an optical fiber, light signals always pass at an angle which is higher than the critical angle. True or False?

The statement that light signals always pass at an angle higher than the critical angle in an optical fiber is false. In optical fibers, the principle of total internal reflection is used to guide light along the fiber. This occurs when light traveling in a denser medium, such as the core of the optical fiber, hits the boundary with a less dense medium, such as the cladding, at an angle greater than the critical angle.

However, in practice, light is often introduced into the optical fiber at angles that can be equal to or less than the critical angle. When the light enters the fiber at these angles, it can still reflect internally as long as the proper conditions of total internal reflection are met. Thus, light signals do not always pass at angles greater than the critical angle; they can also enter the fiber at angles that are precisely at or below this threshold, as long as the overall conditions favor total internal reflection.