A Level Physics Practice Exam

In a fiber optic cable, what are the roles of the core and cladding?

1. Decoupling light and sound

2. Refracting and reflecting light

3. Directing electric currents

4. Controlling thermal energy

The correct answer is: Refracting and reflecting light

In a fiber optic cable, the core and cladding play crucial roles in the transmission of light signals. The core is the central part of the fiber where the light travels, and it has a higher refractive index compared to the cladding that surrounds it. This difference in refractive indices is essential for the process of total internal reflection to occur. When light travels from the core to the cladding, if it hits the boundary at a steep enough angle, it is reflected back into the core rather than refracting into the cladding. This reflection allows the light signals to be transmitted over long distances with minimal loss. Therefore, the primary functions of the core and cladding in a fiber optic cable are to ensure that light is efficiently refracted and reflected within the core, enabling effective communication. The other options do not accurately describe the roles of the core and cladding in fiber optics. Sound is not transmitted through fiber optic cables, so decoupling light and sound is not applicable. Electric currents are not directed by these components as fiber optics are designed to transmit light rather than electricity. Additionally, controlling thermal energy is unrelated to the operation of fiber optic communications.