A Level Physics Practice Exam

What effect does cladding have on the critical angle in optical fibers?

1. It decreases the critical angle

2. It has no effect on the critical angle

3. It increases the critical angle

4. It makes the critical angle unpredictable

The correct answer is: It increases the critical angle

In optical fibers, cladding plays a crucial role in determining the behavior of light as it travels through the core. Cladding is a layer of material that surrounds the core and has a lower refractive index than the core material. This difference in refractive indices is essential for the phenomenon of total internal reflection to occur, which is the mechanism that allows light to be confined within the core of the fiber. The critical angle is defined as the angle of incidence above which light is completely reflected within the more optically dense medium (the core), rather than allowing some light to refract out into the less dense medium (the cladding). When light attempts to pass from a medium with a higher refractive index (the core) to a medium with a lower refractive index (the cladding), it will only be totally internally reflected if the angle of incidence exceeds the critical angle. By reducing the refractive index of the cladding relative to that of the core, the critical angle for light traveling within the optical fiber is increased. This means that the light can be incident at a greater angle with respect to the normal before it refracts into the cladding, thus enhancing the fiber's ability to maintain light propagation without loss through the sides. Therefore,